Asslamo Allaikum,
If someone talks about my mother/daughter/sister/wife in a sexual manner in front of Na-Mehrams and they all laugh about it you better believe that I won't be talking to them!
Wrong or right but I will react.
And if they are talking about some other Muslim Sister I would still talk and forbid this trash no matter whether I know her or not.
We shouldn't joke about Sisters in this lucid, evil, Haram manner. In Islam we respect our Muslim women like our own mothers, sisters, daughters. If we want to marry someone we give proposal according to Sunnah and do things properly. A Muslim woman is not a commodity which should be discussed in the open
I am Sorry but I feel very seriously about these matters.

