I have no problem with 'cause and effect'...Bin Laden knocks over the Trade Center, the US [and others] expunge the Taliban and its supporters. Quid pro quo...
Now. if Bin Laden only SAID he would knock over the Twin Towers, and the US [and others] expunged the Taliban and their supporters 'just in case he rally DID get around to doing it'..[quaintly referred-to as 'pre-emptive striking']...THAT is over-stepping the mark, and no amount of righteous chest-beating will alter the truth of the matter that the instigator of violence is the 'oppressor' and not the 'innocent victim'.
If Saddam is sufficient of a tyrant to oppress his own people and indulge in ethnic cleansing then it is the role of the UN to determine whether it is appropriate for outside action to be taken for the greater good of the world community and/or the iraqis themselves.
Nowhere is there a right granted by some 'almighty being' to empower the US and/or GB to take it upon themselves to intervene. {although the cynical will say it's political expedience.....election year, etc].
Once upon a time, the Imperial Japanese determined that the Pacific Fleet harboured at Pearl was a 'potential threat' to their sovereignty and influence over the region, and conducted a 'pre-emptive strike'.
THAT time, the US responded with a more 'realistic' sense of righting a 'wrong-doing', than they will ever be attributed with if and when they get all 'pre-emptive' with Saddam and his WMDs whether he has them or not.
It may come as a heart-rending realisation that even your OWN beloved country is not necessarily above reproach and incapable of doing wrong or making mistakes.