if you see a popular post where two people are jokingly giving each other shit, it is both possible and extremely likely that these two people are friends messing around. if you approach a stranger with this overly familiar hostile energy, you are not being funny. you are just being rude.
remember that it is both extremely possible and highly likely that op will see everything you add to their posts, including tags. don't say things you would not say to their face.
a post urging people to not be rude to strangers is not a wink-nudge suggestion that people should actually be rude, nor is it a sign that op just needs to toughen up. asking people to be kind is not an outlandish request. if you find yourself offended or see it as an opportunity to show how funny you can be by being mean to someone you don't know, you're just an asshole.
it is much easier to say nothing than to go out of your way to be rude. blocking people is good and healthy. block whoever you want!
posts were more often than not made to express one's thoughts, feelings, experiences, etc. they are not intended to be directed at you, nor should they be taken personally
every account has a person behind it who can see and respond to your actions
if someone stating these things makes you angry, think about why that is