Is it ever acceptable to swear/raise your voice at someone?

[magnoliaa]

Maybe acceptable is the wrong term but is it ever understandable/forgivable and does it always warrant an apology, even if the other person was the one who initiated it?

Hahaha, yes of course. In an ideal world we'd all speak politely and gently to each other in well-modulated tones. In the real world, sometimes these ideal standards drop. I expect people to apologise if they swear at me, though.

I don't think any of us would be entirely human if we'd never raised our voices in anger or sworn. Hopefully though it would take quite a lot to get someone in that state and it would happen very rarely. I would apologise if I had behaved like this even if I was "in the right" but I suppose it depends on the individual circumstances.

Of course. Anger is a completely normal, healthy & often very useful human emotion. More than once, I have had to scream “FUCK OFF!” at some dickhead in a bar who has mistaken my arse or boob for a hand-warmer.