The RIAA doesn't have to sue to make OP's life miserable. They have enough lawyers on the payroll to drown him in perfectly legal demand letters. Go one step further and assume the demand letters are harassment - what's OP going to do, sue the RIAA?

Nahh, for a bunch of annoying letters take them to small claims court. Cheap for you, expensive for them, and you win if they don’t show up.

This is a cool feel good theory but can you show an example of this working?

It’s not the kind of thing that generally makes the news. One example that was is a guy who was making good money doing this to spam callers. His case was bolstered by asking to be put on their no call list and then them ignoring that, but the point is the vast majority of people don’t do it even if in theory they could.

However the important bit isn’t winning in a harassment case but having documentation to get them to stop in the future.

haha, no, this is not their first rodeo

Sure, but that’s why they avoid this kind of harassment in the first place.

You made a hypothetical assuming they would do something they wouldn’t because it puts them at risk.

Exactly, you might just get a takedown notice. Or you might not if someone decides they want to burn you in court. This is how chilling effects from copyright laws can suppress perfectly legal speech.

Suing isn’t just going to court it means subpoenas, depositions, motions, letters, etc. all this stuff costs a ton of money without you even stepping foot in a court. The system is so broken