Is it wrong for me to be pissed off at my husband for this?!

Okay so his sisters fiancé is a total douche bag! He has on three separate occasions blasted me on Facebook and to my husband and myself for no reason saying I shouldn't be married to him and that I'm a piece of shit and he should leave me all while I am 6 months pregnant with my Husbands child. Im pissed off because my husband still talks to this guy! Makes it seem like it's no big deal to talk shit to or about his wife?! If someone did that to him I was be furious and never talk to that person again. I don't care that he's with his sister or not it doesn't matter! We can have a relationship with his sister without her fiancé. What should I do/can I do? Mind you this has happened 3 times!!