I think it would depend on the whole context of the argument. If someone is goading to get a reaction, knowing that the other person is likely to swear back at them, then it is 6 of one, half a dozen of the other.
I quite regularly tell my husband to fuck off. He regularly tells me to do the same, but that is not during an argument, that is just us bickering at each other in a light hearted way.. (ie me "make me a cup of tea while you are up".. him "fuck off" or him to me "you silly cow, you are driving around on a bald tyre".. me "oh fuck off, I didnt notice it"..
However if I spoke to him like a child, or spoke down to him (which I honestly think that telling an adult that "there will be consequences.. ) I would expect a gobful back.. and if someone spoke down to me that way, they would get a reply they might not like either.
IF he is being nasty and abusive towards you for no reason, and not during an argument, or in the heat of the moment, then it is a problem and I wouldnt tolerate it, nor would I expect my husband to put up with me swearing at him either in that respect.
Also, if most of your relationship is spent arguing, not on speaking terms to each other, and with you both struggling to be civil to each other, then it doesnt matter if anyone is swearing, it is time to evaluate whether you want to continue the relationship.