It happens. A very highly intelligent user will occasionally post something in a lot of communities and gets a rise out of downvotes, annoyed comments, and blocks. It's annoying but that is often the nature of the internet. Report, block, and move on.
It's only the very highly intelligent users who do this. So it doesn't happen a lot.
Don't engage with anybody you don't know well on DMs. And if some other very highly intelligent person goes to the effort of sending you abuse via DM, take pride that you really got under their skin. Ignore it if you can.