I need advice please long story 😩😟

My husband is irate and I’m heart broken. I’m 30 and 24 weeks pregnant. My husband is 33. Been married 2 years but dating longer than that.

My younger sister(27) was with a man for 5 years. They have twin boys together and he left her during this past summer. He actually left her 2 weeks after I found out I was expecting my rainbow baby. She went through a small phase of going out with her friends and chatting men up from tinder.

Recently as Halloween, she started meeting up with someone I actually went to school with. He’s 31 ish. Well. Yesterday her and I were on FaceTime and she said “hey -guy- take your shirt off and show my sister”. I thought he was showing me a tattoo bc they were talking about getting tattoos together. Not matching ones but just going at the same time. He took his shirt off and started flexing. It was awkward. I let that slide. Fast forward to today, we are on FaceTime again (I live 3 hours away so we FaceTime as much as we can) and she yells out “hey -guy- show my sister your…” I didn’t hear the last part. I look at the phone and she turns her camera around. He’s in a towel and whips it off and starts shaking his hips left to right to make his private parts swing around. I turned my phone from my view quickly and told her “what if I did that with my husband? That’s so disgusting and disrespectful”.

Now here’s the second part. I told my husband. I was so upset my sister would do that to me. She tells this guy she loves him but realistically they’ve only been seeing each other less than a full month. They’ve already talked about living together. It’s so weird for me bc she has 2 children to worry about and now she’s crossing my personal boundaries. My husband is so angry he wants to rip this guy limb from limb and said that my sister is dead to him. I’m just as upset as anyone and I just feel like this is a huge riff in my family now. My mother sides with me saying how they are weirdos and freaks. And my mom says that my husband has every right to be this angry. I just wish I could find a resolution that doesn’t involve violence. My husband is extremely over protective of me. I want to create space between us 4 until my sister comes to her senses and realizes this guy is just a rebound guy and not someone she will spend her life with. Then try to mend the relationship between her and my husband. But my husband is NOT forgiving at all. Am I wrong to tell my husband how to react? I’m trying to tell him that the level of violence he wants to bring this to is more extreme that what this guy did. But he does not see it that way at all. Do I cut my sister off? I wish she never did what she did. Such a stupid move on her part that now makes me stuck in the middle. I’ll be happy to hear any advice. Thank you all in advance.