Almost never, to a fault
Although, I usually find that I can explain my position in such a way that I don't
need to be unapologetic. Often, it's just a matter of clarifying misunderstandings by analyzing things from the other person's perspective, 'meeting' them where they are, and guiding them to an understanding of my stance (or what I actually meant by something I said) from there.
Usually, if a person really knows what I mean, the issue gets resolved. If I forget to call you but I do care about you, I'll ensure that you don't take my forgetfulness as a sign that I don't care.
Sometimes, well.. screw it. If someone's being an arrogant, insulting jerkface and pushing their stance way too much or 'reading' me in a totally incorrect way and insisting that they know me, I'll sometimes apologize just to end a confrontation, then pretty much have nothing to do with them again. I'm not really responsible for changes that other people 'should' make in their overreaching life perspectives--
I can't change them, and there's no point in butting heads with someone who wouldn't compromise a damn thing, if the stakes are pretty low.
Ironically, apologizing or agreeing in such a manner
is a way of being unapologetic.
When I notice that I start to bend too much, that's when I become truly unapologetic. I'm not going to compromise on very fundamental core values--religious stances and so on.
Compromising on little B.S. daily details? Yeah, I don't care enough about those to make a fuss about them. Anything less is just pedantry.