Maybe build a potato canon to control the pigeons?
Just kidding, sort of.
If the real problem is the pigeons, does the city/county/DNR have a program for trapping and relocating them?
Sadly, people can sue you with no basis. Been on the receiving end of that one. Whether can win anything by doing it or not is a whole different matter. Meanwhile, they make your life H-E-double toothpicks and the attorney rob you blind. If it goes to a judge only, you have a fair chance (not counting the lost sleep, stress, and lost $$$$$ for the attorney) but if it goes to a jury, the person bringing the suit will often get some reward for their misbehavior because juries tend to figure the must be SOME grounds or the suit wouldn't have been brought.
Perhaps you should check into getting a restraining order against this neighbor? That often does not require paying an attorney, just filling out and filing papers with the court. You can find that out by calling the local court. The fact that he refused to respect social distancing in a pandemic and threatened you on top of it should be ample justification for a RO.
You might also try a peace offering and a chat - at 6' or more distance to find out if maybe he's super stressed about losing income and scared of losing his house, etc. Maybe he just needs some help with resources?