Nextdoor is another example. At least with FB or Twitter, it's a opt-in model -- you have to friend or follow someone to see their posts. With Nextdoor anyone can post to their neighbors, so (at least where I live) many people use it as a soapbox to air any trivial complaint/grump/vendetta to hundreds or thousands of neighbors; I see a lot of toxic flamewars on there.

Ultimately I think social media is an amplifier, taking whatever individual or collective insecurities that were latent, and just projecting them for better or worse.

Disclosure: FB employee but only speaking for myself