Are you drunk on social media?
If you walked into a bar filled with inebriated humans and one of them insulted you, it might sting less under those circumstances. After all, a drunk person is not fully capable of controlling what they say.
If someone insults you on Twitter or Facebook, it’s basically the same thing. The users are under the influence of a highly addictive substance and not fully capable of controlling what they say.
(If you feel either of the above scenarios happens too frequently for you, consider the source and/or spend less time in bars or on social media.)