Hugs, Phoenix. First, I'll admit that I don't have the cleanest mouth - generally when stubbing toes on the dresser or stepping on Legos that didn't get picked up, or contemplating XAH's failure to take any kind of responsibility. But I digress. A constant stream of foul language, though, is a really big trigger for my anxiety.
I agree that at 19 and 35, you're not responsible for correcting their language any more, but I think it's more than reasonable to be able to set a boundary on the language that is not acceptable in your home. I'm closer to 40 than to 30 and I think my Mom would still threaten a bar of soap, and she would probably follow through with it if the language continued. (And there's no way I would even think of letting a small curse word fly at Grandma and Grandpa's - even if I dropped a piano on my foot.) And while it's great that your husband is so keen on taking his psychiatrist's advice, there are other ways to express anger besides cutting lose with a stream of f-this, that and the other.