My mother used to call it manners

[underpants]

2. I agree completely and say this all the time

When someone mockingly or dismissively says "oh that's just PC" I point out that it's simply manners. If someone says something is offensive to them you should take that into account. You can still say what you want in your own home or in certain settings but in front of them you now know that saying that costs you in some shape or form. They're not telling you what you can say.