My Dad has never said fuck off/piss off etc to my mother. If he did it would be grounds for divorce. You just don't speak to her like that
When dh and I argue, we throw obscenaties around, me more than him sometimes but I would never be offended.
How about you, are you offended? Would you scream HOW VERY DARE YOU if he swore at you?
(the fuck off thread got me thinking about this)