'The left' doesnt demand submission. A small % of hyper-vocal and aggressive people on the left demand submission. Everyone else on the left just hopes people treat others how they want to be treated and are resigned to teaching their kids to try and be tolerant when confronted with ignorance.The left in its many forms demands a response. They demand attention. Actually, more than that, they demand submission. That's what the whole uproar the last few years has been about. They don't really like the responses they are getting.
I have been accused of being transphobic multiple times in the last 3 years. Its a really wild experience to step back and watch take place. A small vocal and angry % is what you refer to. They are active on social media because it is a platform that is inexpensive, immediate, and wide reaching. That amplifies their agenda beyond the actual numbers they have.