Yeah I'm not sure about banning bottle tops. You'd have to have a real luzz on you to do any damage with one, they're too light and would lose any real pace quickly when thrown.
As you say, all guesswork without seeing the tweet in question. It might've been horrific, and the club might've been totally in the right, or it might've been very soft, and the club has overreacted severely.
Yes, the line is getting harder not to cross, because things are unacceptable now that weren't seen as unacceptable 20-30 years ago. We're trying to make progress and move forward as a society.