Wow, some of you guys don't sound like much fun to travel with! Personally, I don't recite any of the words to the pre-shows mainly cause I don't know them all word-for-word (I guess I'm just not paying that much attention), but honestly, I don't really care that much if others do. Truth be told, everyone is on vacation and there to have fun, and as long as no one is getting hurt or no rules are being broken, there isn't much anyone can do to stop people from doing these minor things that bother you. Perhaps you redirect your energy towards focusing on the subtle details in the stretching room (lots of them that many, even hardcore Disney and HM fans overlook), but you've paid a lot of money to be in that park, so why spend your time getting annoyed with other people's fun? Maybe even appreciate that somebody enjoys the attraction that much that they've memorized the opening spiel.
As for the screaming, something I'm incapable of participating, you know it's coming (it has happened almost every time I've been on the ride), so just prepare for it and cover your ears. I guess what I'm trying to say is this all isn't really that important. Let people have their fun. They're on vacation just like you, and it's only a tiny bother in the grand scheme things, not really even worth a thread on the TPA&S form in my opinion. There are plenty of more substantial guest "tendencies" that are worth complaining about.