I think I made it clear that I support the course we are currently on - building an international coalition to wage war on the aggressors.

The neoconservative plea was but a thinly veiled declaration of war on all of Islam.
Even if not intended that way, that would be the ultimate result.

As at the beginning of the Gulf war, we are at clean slate time - the past does not matter, what does matter is the current response.
If we have proof of Iraqi involvement for this attack or potential future attacks, then we strike against them too. The open letter did not call for that, just attack Iraq now.