<[a] Armed invasion is/was/ever shall be the only way to liberate/disarm Iraq

Unfortunately, this is true. Or at least I have yet to see anyone come up with any plausible alternative to [a], and I have driven at least a few people to distraction when they try to worm their way around that simple fact. Davin for one is about ready to blow a gasket.

[b] anyone who thinks otherwise supports Saddam's evil treatment of his own citizens.

This is a bit of a non-sequitor, as [a] and [b] should not really be connected in a political policy sense (many pro-war people have been doing this too). The word "liberate" really shouldn't be in that part. The policy reasons for disarming Iraq were not related to how he ran his own nation, except maybe insofar as the sort of person who would feed live people into a chipper may be exactly the sort of person who would sell or give nerve gas to anti-American terrorists.

Now, if we are talking about the liberation of Iraq as a consequence (bonus?) of our military action, instead of a primary goal, then [b] becomes applicable.

And sorry, but it's true too, if you are listening to all the people complaining about how awful Iraq has it now, while paying little or no attention to what it was like before, or what it would have been like in the future had we done nothing.

To be sure, I myself would not use the term "supports." The word "tolerates" would be better. "Ignores" would be the best.