How about "Wow. Your husband is really good in bed." or "I'm sorry."? Obviously, you are not comfortable with what you are doing with her husband or you would have no trouble talking to her.
it turns him on... and if the wife wants him to talk nasty then tell him
You should talk to your wife.
Only if you can live with the answer.
NO!! she can go where she wants
They should always talk about it to their wife's first
He had lovers of both sexes, but no wife.
As often as both he and his wife wants to.
Persephone is Hades' lover, and wife.
Confront the husband first, then talk to the wife if the husband doesn't stop.
He is married, respect that or you will be the next one in line for heartbreak.
Then he should take his girlfriend.
Talk to her about it and discuss how the two of you want to live.