Why YSK?
The first person who typed “should of” probably heard of it in real life that was meant to be “should’ve”, they typed “should of” online and readers thought that it’s grammatically correct to say “should of” which is in fact wrong and it became widespread throughout the years on Reddit.
I hope something could start to change.
It really depends on the context whether or not it’s appropriate to correct someone
Oh yes, 100%. Type of conversation and relationship between partisipants are important to consider. I just believe that the attitude that correcting someone is a negative thing is wrong. Sometimes it might be, like you say, depending on context, but not in general