I stand corrected. Thank you sirs.
Just don't say "case and point" or "for all intensive purposes", or we will be fighting.
"all intensive purposes" still sounds more correct to me because "intents and purposes" just sounds redundant. So I just don't say either.
Another "correct" expression that annoys me is "You've got another think coming", which I had always thought was "You've got another thing coming". The former bugs me because "think" is normally a verb not a noun. Yes, the latter is needlessly vague with "thing" but I just figured it was intended to be a nebulous threat that doesn't mean anything specific, like "or else".