I'm not calling for a boycott, nor have I stopped drinking American whiskey.
However, international boycotts put a lot of pressure on the former South African regime, and, indeed, that country is now using it as a protest tactic against the war in Iraq.
Nobody can say they are no longer going to buy products produced personally by George W Bush, so you have to let him know in other ways.
The government's actions were outside the average American soldier's control, yet he or she has to go out and risk their life in the war. I think that if you felt an American whiskey producer would have to suffer a little to relieve the vastly more significant suffering of those in a country such as Iraq, then it is worthwhile.
That said, I respect your opinoin on the matter and am not trying to get people to boycott... I just think it is a legit tactic if your trying to influence policy.