Not really comparable. If in 2003 the US did nothing Iraq would still be doing what it was doing and there would have been no war. If Ukraine stops fighting for even a day the country no longer exists.
It isnt special pleading when you can point out major differences between cases.
Kraut IMO made a pretty good argument based on exactly that point that Iraq would have been doing what it had been doing already,
That being that what Iraq was doing was plenty horrible on its own, and that Bush and co could have made an argument for US involvement just on the merits of stopping a genocidal dictator. The question with no answer is if the public would have accepted that argument for going into Iraq at the same time as Afghanistan.