Yes, it's called a moral judgment. It's having an opinion on right and wrong and not accepting wrong just because the other person thinks it's okay or somehow justifies it in their own mind -- that's what people do. Everyone does it, because everyone has things that they believe are wrong. We may differ on where we draw the line, but everyone has a line where they're going to label the actions of those on the other side "scum" or worse.
This concept of accepting differences that's so popular these days is all well and good, but it doesn't mean I'm required to accept or tolerate a difference that I believe is morally wrong -- if that were the case, then murder would be legal if the
murderer didn't think it was wrong.
For me, the line is simple: deliberately doing something that you know will cause harm to an innocent is wrong.
If someone knows their partner will consider an act infidelity and does it anyway, thereby hurting their partner, then I believe that's wrong.
I label them "scum", just as I label murderers "fucking scum" and pedophiles "fucking scum who should go feet first through a wood chipper" and label someone who hurts those I love as "fucking scum who
will go feet first through a wood chipper" -- it's simply a matter of degree. (Obviously I'm not serious about that last one. I would never use a wood chipper ... a few days in a mangrove swamp is so much less messy.)

My point is that we all have a line and a hierarchy on the other side of it -- or can you honestly say that don't don't label those who rape, murder or are pedophiles? Or that you wouldn't label someone who hurt a loved one of yours as worse than that?
For you, apparently, the line's in a different place than mine. Just as my line's in a different place from those who think BDSM is wrong and label us -- but it's their right to make that judgment, just as it's mine to set my line. I may think they're misguided or incorrect, just as you, I assume, think I am. And you're welcome to try and convince me of that -- just as I'll try and convince them that the line should be at "harm" and not at "I don't like".