"Ever" is a very strong word for a technological project which doesn't contradict any known natural laws. Do you honestly not see the possibility that we might be able to build a self-sustaining, comfortable colony on Mars in 100 years? 500? 1000?

I honestly do not, for the reason that the cost of such a venture is simply too high. If we cannot even manage to bear the minimal costs of stopping catastrophic climate change on our own planet, then what makes you think we will ever have the will, much less the ability, to undertake the terraforming of a lifeless planet millions of miles away?

I'd be curious to see a rational argument as to why this couldn't be the case.

Do you have a source for that? :-)