I'm not suggesting there's no place for the boo, the jeer, the catcall. Polite applause at appaling displays do no one any favours. But the distinction I would make is this: if a speaker were, say, accusing Natasha Stott Despoja of grandstanding then I would hear them out since that is a real possibility. If they got insulting about it and said she was a 'media tart' I might get offended. The line is crossed when you start colouring your terminology.
Additionally, if the claims can't be substantiated, or it will take a while to unravel the discourse that justifies your attack, then a modicum of restlessness in the audience is permissible. In this case, it could occur if Doctorow had opened his speech by stating that the Bush administration 'allowed 9/11 to happen'. His argument here might be that, while such a fiendish plan naturally took the rest of the world by surprise, it can't be said to have done so in the case of parties who were given specific and repeated information about the intended action beforehand. True enough as it stands but difficult to relay in a short acceptance speech. Better to document this in a report where all the necessary links, quotes and references can be made.
But stating that Bush started the Iraqi "war" on a false premise is unassailably true so it behooves anyone with a scintilla of manners and respect for natural justice to hear the man out. Not a point that any of the rabid Bush supporters are even capable of comprehending.
I also don't buy the accusation that it was 'inappropriate' to make a political speech at such an occasion. Doctorow tied it to the points he was making and, as a guest speaker, he must have some lieuway to choose his topic. There could hardly be a topic more pressing to deliver to the youth of America when many of their number are being killed overseas and they are under threat of being enlisted themselves. It is more of an abrogation of responsibility to do as the mainstream press is doing and going soft on the Bush position.
Keep your boos locked away for such things as:
1) the lead singer of Brian Jonestown Massacre behaving like a wanker (apparently he does this sort of thing often)
2) reality shows that set guys up with a 'stunning chick who turns out to be a bloke' or any other combination of humiliation and degradation that's out there.
3) cynical 'by numbers' art such as songs that repeat 'baby', 'never gonna give you up' et al and cop shows and medical dramas
4) transparent lies and distortion
5) idiots who scratch graffitti on the train windows
6) people who take littering that one step further by smashing glass on the footpath thus creating the possibility that an animal or barefoot child will cut themselves
The list could go on forever and never reach EL Doctorow but would probably include Bush apologists who try to shout down the facts. I'm pretty sure of it.