I think you're missing the crux of the point: why is anything the Trump administration says taken at face value? They have no commitment to the truth, whatsoever.

If Iran was on the path to developing nukes, the correct path here was to:

1. Show the evidence to congress, and declare war legally based on the facts.

2. Get international buy-in, and work with our allies (all of whom would very much like to prevent Iran from procuring a nuclear weapon).

This was a hastily started war with flimsy goals and seemingly no real urgency. And one of the first things we did as part of our attack was to bomb an elementary school, killing hundreds of children.

Critics of this war aren't "hell bent on not preventing the spread of nuclear weapons". We're mostly looking at the situation, and thinking "this is not great".