
Whether or not its offensive is pretty much irrelevant, because the function of correcting someone's technical mistakes in RP--whether it's spelling, grammar, malapropisms, or what have you--is superfluous, at least to me.
My own thought process on it goes like this:
Is the meaning of their sentence or sentences clear?
If yes, then don't bother, even if it's incorrect.
If no, then ask for clarification, proceed as normal.
If the meaning is misinterpreted, then that is an opportune time to bring up spelling, grammar, malapropisms etc. without it being needlessly critical.
My own thought process on it goes like this:
Is the meaning of their sentence or sentences clear?
If yes, then don't bother, even if it's incorrect.
If no, then ask for clarification, proceed as normal.
If the meaning is misinterpreted, then that is an opportune time to bring up spelling, grammar, malapropisms etc. without it being needlessly critical.