My theory on this is that by being so virulently anti-USSR (and anti-USSR allies), trots during the cold war pretty much always found themselves aligned with US interests, as well as being very comfortable with anti-USSR propaganda at home. This meant that their bedfellows, especially in The West (tm) wound up being... Well, the worst sort of person that would invade Iraq and be uncritical of US foreign policy. To say nothing of what that would do to your internal thoughts (which... Who could speculate for any individual trot).