Is there really any significant difference between "it seemed a good idea at the time" and "the reasons for intervention in Iraq were totally justifiable at the time"?

I suppose the former expression can be taken as implying that the action was a bit spur of the moment, and the latter suggests that it was more of a considered decision. But if you were in a court of law, charged with criminal damage, I don't think it would make a great deal of difference which way you put it.

Pedantic note: Reasons can be valid or not, and "intervention" can be justifiable or even justified. But reasons can't be justifiable or unjustifiable.