In an interpersonal (small group or 1 to 1) context, sure, I agree, if you know someone finds something offensive and you keep saying it, you are kinda being a dick (at the least) even if you don't think you are being offensive.

But beyond that.. what you are saying is not is just not practical or reasonable. You can't realistically stop using every word or phrase that someone somewhere finds offensive.

We live in a time where everyone is offended by everything and everyone defaults to the righteous victim role (and this is not some veiled criticism of the left, the (American) left gets criticized for this all the time, but in my experience the right can be even worse (more easily offended, more fragile, more eager to play the victim, e.g. 'war on christmas', 'christians are an oppressed minority' and all that bullshit).

My opinion is that you should not change your language because someone else is offended by it. You should listen when someone else is offended, try to understand, and be considerate. If you come to understand that what you said was innapropriate due to that conversation then change your language, but if you don't agree, don't change your language just be more considerate around that person because they are sensitive to it.