There should be a chat restriction that allows the streamer to restrict chat to all or some of the viewers, based on how long they have been watching. Similar to how Follower Only chat allows the streamer to restrict chat to all or some of the stream's followers, based on how long they have followed.

I think even a 5 minute timer before chatting would deter a significant amount of harassment, and it should have less of a stigma than Follower Only chat.