Yeah, that comment they don't like? Crazy people will false report some incident to get a SWAT team at your address. Other crazy people will call your employment and start a campaign of attacks to get you fired. Plenty of examples of this out there. Some people, eg youtubers, get swatted multiple times. Police turn up multiple times. These aren't isolated cases.

Here is a non-nefarious situation:

Let's say your side project is for a political party. Then, two years later, you apply for a job and the hiring manager is from a different political party, and has strong views on the matter. You don't get the interview.