I blocked as many people as I could, but when it's random people on facebook sending messages to tell me what's going on in a situation that's playing out in real life & one I'm trying to distance myself from, you can see why blocking was not an option - as fast as I blocked someone, there would be someone else to take over. At least with Whatsapp people have to have your number, unlike on social media where you can be found by just about anyone who knows your name.
I solved the problem by closing my facebook account and opening another in a name that no one would know to look for.
Facebook messenger was the worst, because as soon as someone (anyone) opened up a message and began typing, my phone would make a brief "popping" sound. I would then look at my phone with my heart racing, waiting for the message to appear. Sometimes it never did appear, because as we all know it's perfectly possibly to accidentally enter some text while reading messages, so I'd hear a pop and then be like a cat on a hot tin roof for hours, waiting for a non-existent message to appear.
If a message from someone who means me no harm is sent to me and I don't want to deal with it, then I don't. But I accept also this could be a generational thing too, as I come from a time where the only telephones we had were tied to a wall in the house and the was no way of knowing who was calling to say what until the call was answered. There was no caller display, and no chance of getting the number before the year 1995. Everything was much simpler then, and we had to develop a resiliance, although on the other hand every call was charged by the minute, so people didn't just ring about every single thing the moment it popped into their heads, like we can do now with whatsapp & messages. And added to which, it was very socially unacceptable to call people at certain times of the day, or the week, or when you knew they were in the middle of nervous breakdown crisis.