Not really understanding something here?

That was a great book, wasn't it? People are going to heckle, no matter what. My feeling is that if you want to go to a presentation, you should only do so if your goal is to learn. If you want to argue, skip it. The same kind of thing happens when political speakers come. Why someone would go to a vegetarian/vegan event, talk, forum, etc when they had already made up their mind, or didn't actually care about learning something is beyond me. The same should go to both sides. I would never attend a talk about crush videos because I find it disgusting and am horribly opposed. I couldn't learn anything useful from it and I feel so strongly I know that I wouldn't change my mind. So why ruin the experience for people who are actually there to learn?