Is OTHER wrong in the post ? POST : Ok so i have been with my SO for years. We were chillen at a house party when BIL and his girl are being obnoxiously affectionate (ass grabbind,kissing ect). I tend to ignor that because i just find it weird to do infornt of people. 
 So we sat down to watch the game, everyone's buzzed and full when SIL taps my shoulder.  "Hey are you guys together"

Me-Of course I am why?

 SIL "Well it seems like you guys are just friends like you guys are together for like other reasons so she's like you guys don't seem like lovers you guys seem more like gay friends who live together to tell people to not hit on you guys."

I'm already buzzed and I just started laughing "like what do you mean why would you think that?"

SIL- well you guys are so unaffectionate. I've never even seen you guys hold hands,no kisses or anything? like how can you say you love each other?
I was gone laughing "okay yeah I guess we're in gay and lesbian lovers. " I can't make it fun of the statement and laughing elaborating saying we must never touch each other and must have never hold hands it's so inappropriate for roommates.
 SO look back at me and BIL looks very awkward/ slightly embarrassed. 
BIL chimed in saying SO never been the kind of person who shows a lot of affection in public it's just not something that he does. I can see that my Asos visibly upset but I couldn't take it seriously at the moment because in my mind she had to be joking. Couldn't be a serious statement just because you don't see someone's sexual behaviors doesn't mean they don't love somebody. 
When we git home SO confronting me. saying he couldn't believe what happened and it was very offensive. But I told him that there was no reason for him to worry about that that other people's opinions don't really matter and we know what we mean to each other. 

I told my best friend about it and she got mad at me for saying that I should have stood up for him and our relationship but I really can't see it as a serious moment. Am i in the wrong?