> "I don't think X" is often and "correctly" used when the logical meaning is "I think not-X".

Quite true, and it explains why it took the human race a hundred thousand years to develop the syllogism.

Even now it takes close study for even university students to get deductive reasoning straight, and all of us still stumble now and again. Darn that consequent!

A big "however," however, is that everyday life and speech do not usually carry the burden of careful and explicit deduction required by scientific and technical applications.

Maybe the world would be a better place otherwise, but pointing out the illogic (why not "ill logic"?) of widely used and understood idioms would be a thankless and full-time job.

When I was in school, we were warned never to use "contact" as a verb meaning "get in touch with." Why "get in touch with" was OK, but "contact" wasn't, remains a mystery. Few people seem to have paid attention, and decades later the ban sounds arbitrary and nonsensical.

The only usages worth objecting to are those whose (shouldn't that be "whiches" or something?) patent absurdity makes them truly distracting ("Walking down the street, a pub came into view"); those that   make you look like a jerk for writing them("Dont need no edjikashun, dont need no thot controll"); and those that are more or less incomprehensible.

There is (or is it "are"?) a handful of words like "irregardless" and "decimate" that have somehow attracted special scorn over the years, and, yes, for that reason they should be avoided in careful writing.

The bright side is that most people do want to avoid such things. But as for trivial examples, they "could care less."