When somebody says something offensive to a well-adjusted person, do you know what they do? They shrug it off, because words are just that.
For some less-adjusted people, it seems an offensive statement is an existential threat of sorts.
Unfortunately, social media concentrates the less-adjusted people as well as the well-adjusted. It's just the less-adjusted have plenty of time to spend on social media.
It also doesn't help that most people don't really spend any time developing their mental resiliency as a child because educational environments are overly protective.