The worst wasteland on earth is far more hospitable. Let's look at the ecological damage to this planet this effort would cause, and see if there are more or fewer places for people to live afterward. If we think Earth will be uninhabitable in a few centuries, how long would it take us to ruin an unsuitable planet? Is Elon's dream to make us serial killers of worlds, or just to abandon the less greedy, more cooperative people at every stop?

Well Said Bob Stuart, my sentiments exactly...

There is no 'great place' to live on Mars, everywhere is potentially lethal. Even the worst places on Earth are infinitely better, at least you could breathe. No oxygen, no water, no air pressure, arctic temperatures at the warmest, and frozen carbon dioxide at the coldest, do not make a 'great place!' When a rover can produce just one litre of water suitable for drinking, and one cylinder of oxygen, with enough to last one day, then I might believe that colonisation by humans is possible. The best plan would be to send robotic 'settlers' to prepare any selected sites for human occupation. The technology for it already exists, it just needs adapting to Martian conditions. If, and only if, the robots are successful, should any humans attempt to colonise, unless of course, they have a death wish.

People on Mars will need places to live before they get there. No point in going if there is nothing to do either. A lot of infrastructure needs to be in place before the first settlers arrive. Musk is building the transport system. Others will have to work on infrastructure.

I'd like to volunteer 537 people for one way tickets.

This man Elon Musk reminds me of a certain George Donner, and his Hastings Cutoff. The results are likely to be significantly more tragic, as there is no 'spring' to look forward to on Mars, to then attempt to reach safety.

You have to crawl before you walk. Colonizing Mars is like trying to run before you crawl. An off earth city should start with an orbiting city here, close enough to send help, while we learn how to exist off earth. Cities at varying distances would give us launch points for "world ships" which are independent. Next they could orbit the moon and mars to explore for habitation. Short visits from orbit could allow fact finding missions. This step by step method would be the safest, and in the end, the fastest. A more ambitious attempt that resulted in 100% fatalities would be psychologically and financially devastating. And it might so strongly prejudice opinion as to cripple and delay continued exploration, e.g., the Hindenburg disaster.
However, whatever the fastest method is, that would give our species the greatest chance of survival. Leaving earth is like leaving the womb. Earth was a great place to being our journey, but staying too long would certainly be fatal.

In a couple of hundred years, Mars may get to be like Kim Stanley Robinson's "Blue Mars" and be much more desirable for humans than the Earth. The erect posture of humans is much more suitable for .4 g than 1 g , at the average height of about 6 ft. There is plenty of nitrogen in the outer solar system to teraform Mars and it is easily accessible with fusion powered rail guns. The magnetic field is mostly important for protecting low Earth orbit, as the particles come in near the poles to be absorbed as the aurora.

The moon is closer, has water, and has commercial viability, including mineral resources and potential solar power collection. Why even consider Mars before the Moon?

AND ... once again, we have the usual flood of nay-sayers. Unbelievable! Where's your sense of adventure, your human desire to explore, push back frontiers, discover the universe, "boldly go where no man (or woman) has gone before"? If we humans were all like you guys, we'd still be huddled in the relative safety of our horrid little huts in the dark ages, growling at the world from the hearth-rug. Don't you GET it?? This project is the very essence of humanity.