The 'children of christ' group has hired a somewhat well know 'biologist' to give a talk on intelligent design. Is it legal to film it (for the purposes of debunking and youtubing later)?

This quack is really obnoxious. I’d enjoy putting the talk in its place. He has a habit of using big words to say little things, and doing a very careful bait-and-switch with his uneducated audience. He touts around the ‘fact’ that he’s published 600 articles…. which is realllllly stretching the meaning of ‘article’.
I’m not intending to crash their silly party… i’m just intending to rip it to pieces later. I have my doubts that its going to be hard to do.