I don't see why you shouldn't be allowed to.
And in the context of the game (i.e. war, and killing other armies), a small bit of swearing should be perfectly acceptable.
The context you use it could also an issue though. e.g.
Calling someone a silly ass = acceptable.
Threatening to something something up someone's ass = unacceptable.
Commenting one someone's nice ass = possible sexual harassment.
As long as it's not intended to offend, insult, or cause distress, I think it should be fine.
FREEDOM!!! of speach