Or not, but if he was would it matter to vegetarianism in general. Would it be an indictment of vegetarianism? I think not.
There is a post on an ethics blog about how saying that Islam is responsible for Bin Laden's actions is different than saying vegetarianism is responsible for Hitler's actions. The reasoning is that Islam is a religion open to violent interpretations.
While I agree that Islam is open to violent interpretation, as evidenced by the fact that people interpret it in a way that allows for violence, I think this is true of nearly every religion and ideology minus those that are explicitly pacifist. Being vegetarian isn't and ideology, nor is being atheist, despite the arguments form some theists otherwise. Islam of the form Bin Laden subscribes to is an ideology. I am at a loss to find a single political or Religious ideology which has been implemented on a broad scale that has not been responsible for some level of violence.
This is not to say that Islam is somehow less violent. I don't think that Islam is anything, it's a book and the sunna'. There are a number of interpretations of Islam that allow for violence, as there are interpretations of nearly every ideology. Look at the war in Iraq. One might argue that the justifications given by Bush about democracy and human rights are not "really" democratic or Liberal arguments, but that strikes me as a "true scotsman" argument. It is clear that Liberalism can be interpreted in a way that allows for destruction on a massive scale, but does that indict Liberalism or those who use that interpretation?