Why do people act like if you oppose a single unjust war, you must then oppose all war under any circumstances in order to maintain ideological consistency? 
It is inconsistent to oppose a war for reasons which are no less of a factor in a war you support, and unseemly to do so when motivated by partisan politics. If the reasons many opposed the war in 2003 were valid, they should be just as valid now.
These reasons include, but are not limited to:
- Wars are costly, and not worth the money and lives expended when not facing an existential threat
Stop right there. Is it not possible for someone to see ISIS as an existential threat, but not to have seen Saddam as one? Granted, many people saw him as one at the time, but that was because of faulty intelligence (putting it nicely) about his mythical WMDs. Your feelings about the Iraq War weren't uncommon. It had massive support at first, then fell into the doldrums later. It's not irrational or ideologically inconsistent to believe the president and support his war if you really thought Saddam had WMDs, then change your mind and realize it was a mistake once it became apparent that was clearly not the case.
Anyway, I do agree with you that a solid case must be made, with a clear plan and international backing before this option should even be considered.
