Most modern linguists consider “should have” to be a completely valid variation of should’ve / should have.

Yes, it does contradict what your english teachers in school taught you, and according to that world view “if we don’t have those rules then we wouldn’t be able to understand each other”. But the hundreds to thousands of languages where those rules don’t even exist and people understand missing/“incorrect” meaning from context, as well as the fact that you can proudly stand on your “i know what’s right” soapbox and say that “should of” is wrong, only serve to prove that these rules aren’t actually rules or part of the english language and are more like the linguistic equivalent of fashion.

Again, you understood exactly the meaning OP meant, enough that you could confidently barge in and tell them they’re “wrong”, and tell them what they should have used instead to fit your fashion rules.

Basically, absolutely nobody saw this meme, saw “should have” instead of “should have”, and thought “hmm, i don’t know what’s supposed to be being said in this case.” You dislike “should have” because you were told you were supposed to, and that if you didn’t stick to these rules nobody would respect you or understand what you’re saying. Now, you do the same thing and lose respect for people who didn’t (while also understanding what they are saying exactly). That has nothing to do with the language, and is, again, more akin to “you wore white after labor day” or “you wore socks with sandals” or whatever other fashion faux pas you committed — none of which are related to actual linguistics or the natural way through which languages evolve (or whether or not your outfit looks good on you on any given day)