You're right, Nikolai, there's nothing wrong with 'shouldn't have', but Scher's shudder, with which I heartily agree, is over 'shouldn't of'. It's mostly heard from young people who don't seem to appreciate the nature of their error or are just lazily indulging in slovenly speech. They use 'might of' in the same way.
Using 'like' every few words sets my teeth on edge, as does a rising inflection that turns every sentence into a question: 'Like, I went out last night(?) (You understand what I've just said?)'.
A few years ago, the phrase 'By and large' was overused to mean 'generally speaking'. It always made me laugh as it was a nautical term from the days of sailing ships and referred to a rather tricky manoeuvre to make the maximum use of the wind.