This is another good point. I didn't actually intend to make this point, but I wanted to thank you for pointing this out.

I am not a sociologist, just a layman. But I feel that there seems to be two axis of communication. Mass (you don't know who you're talking to) vs targeted (you do know who you're talking to, like friends). Then, professional (you try to be unoffensive) vs casual (you have no such obligation).

Before the Internet, generally communication happened either mass-professional (e.g. TVs, newspapers, magazines) or targeted-casual (e.g. chatting with friends and family). This reduced offense, since mass channels were largely unoffensive as you said, while targeted channels knew how to avoid offense (i.e. you knew how to not offend your friends and family).

However, the Internet enabled a lot of mass-casual communication. And this created a lot of offense, because you didn't know who would read your messages (i.e. Twitter posts), while you didn't have the professional obligation to make sure it was unoffensive and easy to understand. This created a lot of misunderstandings, offense, etc., which leads to cancellations, hate mobs, etc.

Do note that once again I am not a sociologist, and there seems to be holes in this view. What about large group gatherings? Trashy magazines? Clubs? They seem to be examples of mass-casual communication too.