One of the great misconceptions about linguistics majors is that we like to go around correcting people’s grammar. (That stereotype properly belongs to English majors, if anyone.) So, just to be clear:
I will not correct your grammar because . . .
1. It’s rude.
2. I don’t care.
3. I might be wrong.
4. It really doesn’t matter.
Under certain circumstances, these rules don’t necessarily apply. I might correct your grammar if . . .
1. You are a nonnative English speaker who is trying to improve your English.
2. You are highly grammatically or linguistically aware, and can hold your own in a grammar debate. (Even then, I’m not overly troubled by colloquy, but I’d probably point out a hypercorrection.)
This is what actually does go through the mind of a linguistics major when they hear a bit of nonstandard English:
1. Did she really say that? (Observer error.)
2. Does she always say that? (Performance error.)
3. Is this a consistent phonological shift? (Different accent.)
4. Is she a native speaker of English? (L2 error.)
5. Does she have brain damage? (Some neurological conditions cause specific types of errors.)
6. Does everyone say that where she comes from? (Regional idiom.)
7. Does she form other such expressions along the same grammatically consistent pattern? (Dialectical difference.)
8. Is this part of a larger linguistic trend in English as a whole? (Today’s pet peeve is tomorrow’s standard usage!)
By this point, I’m either musing on the nature of language in the abstract, or possibly I’ve come back to the conversation and am desperately trying to catch up on what she’s talking about.
Either way, I’m not correcting her grammar.