Ever since using the internet, mainly social media, I've dealt with some people online, whom I will NEVER meet in person or talk on the phone with. Every once in a while, I'll come across, say Twitter followers, YouTube subscribers or any other social media, (Even back then when I used Myspace & Facebook) who INSIST on following me, but they try to dictate or control what I should post, & then make me feel fearful or scared to post anything. Everything I post bothers them or sounds foolish. Why don't you just unfollow or unsubscribe, if you don't like it? Well, blocking is too harsh & unnecessary. Also comes off as HATEFUL, in that instance.
Blocking is necessary in cases of spam or harassment/stalking. Sometimes, online narcissistic abusers abuse & exploit the block button, to exercise power & control over the victim, & make the victim feel like he/she did or said something wrong. Especially when you speak the truth, & they're offended.
& then, if you call them out on their abuse, they have their smear campaigns lined up, to get many flying monkeys AKA cult followers onboard to cyberbully you & put you in such a depression that it interferes with your daily real life. This can affect your job or school performance, sleep, family/friend relationships, eating & hygiene habits, etc.
People with narcissistic personalities online feel like, once you put something on the internet, then it's public, & that THEY have every right to do whatever harm they please towards you. Ex: You post a picture of a slice of pizza with unique ingredients, & then an online stranger bullies you, insults you & then gives you unsolicited advice. When you stand up to them, they stalk, follow & harass you everywhere online, & they LOVE IT when they do it on websites where you can't block them! You'd be amazed at the petty reasons why a 65-year old would cyberstalk or bully a 25-year old online.
People online thrive on your hurt & misery. Some people go through a lot of abuse in their household & have no one to turn to for support, so they go online, where millions of people go, trying to seek emotional support & advice, only to be hurt 10 times worse.
Years ago, some people used to say, "Don't take them seriously. It's just an avatar". But these are real people hiding behind computers. Anonymous cowards who wouldn't have the balls to tell you all that to your face.