Why It Is so hard to colonize mars?

Remember Biosphere 2? If we cannot survive on Earth in a sealed environment. Why the hell would anyone expect mankind would be able to do it on Mars? There should be a solid push to do this on the moon first, where help and resupply are only 2 days away. Hell, we haven't even landed people on the moon in over 50 years, if we did it at all in the first place. There is still no reasonable explanation of how the Astronauts survived cosmic radiation. Or how the lunar lander made multiple perfect landings and take-offs when it was never was able to, not even once, on earth. There is also the whole issue of how all the data was lost and the film was copied over, like copying over tapes of your wedding day. And the subsequent nonplus reaction of the Astronauts being interviewed, post return to earth. What happened to fiscal responsibility, while we Pay the FED trillions of Dollars in Interest on our own Money, might as well run a siphon hose from the Treasury to the World Bank. Seems to me just more justification for someone to make a lot of money by lying and robbing precious resources needed elsewhere here on earth or on a return trip to the Moon. Or cleaning up all the space junk or cleaning up all the plastic in the ocean. Mankind is acting like teenagers, that refuse to clean up their rooms or their own messes. At the same time, we are trying to explore the Universe for Habitable planets to colonize, we are destroying the only known source of life in the Universe. With dozens of specimens going extinct daily. The Love of Money, unbridled Capitalism without restraint, is the root of all that is evil within and outside of mankind. GREED, one of the 7 deadly carnal fruit of the flesh and one of many that the Churches are Preaching as Good Holy Righteous and of God, such as the Power of Pride the Fear of Evil and the Hate of Satan as the Great Enemy, thus the cup runneth over, filled to the brim with these emotions created by the heart. "Wealth is proof of righteousness", "Prosperity Dogma", and Santa Claus (Satan Claws) in full Agreement, judging the Richest as the best and the Poorest as the worst. While God remains the deaf dumb and blind fool deceived by the Wolves that pretend to be the Sheep. The opposite of what the Messiah teaches the Disciples, "You Rich have your reward and will have none of Heaven".

Several mistakes: "Mars goes around the Sun almost twice as fast as the Earth." - No, Mars is slower and has a larger orbit. It takes Mars 686.98 days to orbit the Sun. 
"It takes almost 2 years for the smallest distance from Earth to Mars to occur." - No, it's slightly more than 2 years, 26 months to be precise.
 "150 days to reach Mars... It could be a trip of 300 days or more." - A free retrun trajectory is the safest, so most likely. In case an accident like Apollo 13 happens. It means astronauts can return home without burning fuel. It would still take months to get home, but they would. That means 180 days (6 months) one way. And you have to wait for the planets to align for return. That's 26 months round-trip, slightly more than 2 years. Cutting time on Mars drastically and swinging past Venus for the return, that can be cut to slightly under 2 years, but just barely. 
The worst: "If you've ever seen the movie The Martian, you'll remember the ship they used to go to Mars twice was massive." - Hollywood loves giant mostrosities. That ship was about as large as a US Navy Oliver Hazard Perry-class frigate which had a crew of 176. Yet Hermes only carried 6 astronauts. More realistic: Mars Direct habitat, designed by Martin-Marietta, an actual NASA contractor. It would have been the same diameter as SLS core stage. The habitat upper story would have as many square feet as a 60-foot class A motor home with slide-outs. Lower deck would be airlock, landing engines, life support equipment, and a garage for the rover, surface science equipment, and inflatable greenhouse. 
"Testing for this type of craft would take years, and possibly big jumps in technology to make it work." - No, we've had the ability for a long time. In the early 1970s, after Apollo 11 and while Apollo was still flying to the Moon, NASA worked on getting humans to Mars. They had an upgraded Saturn V, modified Apollo CSM, new heat shield, etc. They didn't yet have a Mars lander or life support for that duration, but that's all. In 1990, the Mars Direct mission plan showed how to do it. We've had the ability to go to Mars since at least 1990. 
"We'll need spacesuits and living areas with their own regulated gravity." - Wrong! You get used to your home. Apollo 11 only spend a few hours on the Moon. But if you live there, you get used to it.
 "Mars has no breathable air. So any time a person goes into the expanse, they have to wear a suit. Every time they go into a habitat zone, it has to be pressurized so they can take off their helmet." - Not a problem. I live in Canada. We wear a parka to go outside in winter. Every building is heated, and every public building has an airlock. It's not pressurized, but weather stripping makes it as air-tight as possible. So how is Mars really different?
 "Any program would want to find these potential life forms, study them in every way possible, and not send anyone to Mars until it's clear they won't be harmed." - Again, wrong! Robots have incredible difficulty finding life. Or finding much of anything. A human crew on Mars could do more science in one day than all the robots have done to date. To find life, send humans. And scientists study potentially harmful bacteria all the time. We know how to handle samples without contaminating either the sample, or ourselves. "
#1 Nothing Can Go Wrong, At All". - Wrong. Absolutely every Apollo mission had something go wrong. Only Apollo 17, the last one, was perfect. Every other mission worked around the trouble, and continued on. We'll do the same.

It's unlikely that a life form on Mars would pose a biological danger to us. We evolved separately, therefore work very differently. Life tends to evolve based on what's around it - if anything, life on Mars may never have seen DNA that looks like ours, nor organic composite. It's highly unlikely it would infect us, or eat us, simply because life eats what's around it to survive, not things it never saw and had no way to knowing it even existed. 
 
The only way this could be false that I can think of would be if it released some sort of toxic (for us) molecule. Even here on earth - compared to the insane number of bacteria and viruses and small organism, the fraction of these which are actually bad for us is crazy small.

We will colonize Mars eventually, although Venus is a much better choice. And floating cities would be much more awesome than living on a barren rock with almost no atmosphere.

 

It’s obvious we are going loose people by going to mars, but we can’t solve all the problems thinking about them. Elon Musk is got the right idea. Just fucking do it already and stop with the fucking negativity. We already have the technology to go to Mars and we been able to do it for a long time. Most of the technology SpaceX is doing was already thought of by someone decades ago but was trashed due to budget. SpaceX is not government owned and is a private company able to explore these ideas. Its really sad because these technologies being created are 40 year old ideas already thought of. I’m super glad Elon Musk is brining us closer to where we should be as a species. It’s even brought me to the realization that it’s even possible I could stand on the red planet and look beyond.

If there would be life on Mars, we wouldn't even colonize it, so we don't contaminate it. That's why NASA decided to crash Cassini into Saturn or Galileo into Jupiter for example because they didn't want to take the risk that those probes collide with one of the moons and contaminate it.

IF, a scientific team were to go to Mars and discover life in the form of microbes, they will realize they have sealed their fate. They could never risk coming back.