Acceptance of abuse is not tolerance. It is just abuse.
When it comes to BDSM the line becomes murky. The basic guideline is "Safe, sane and consensual" but all of those words mean different things to different people, even consent. This is why communication is critical in all relationships, but even moreso in BDSM. I've had someone come in from out of town to play and then refuse to communicate with me. They had some fantasy of me simply doing things to/with them. But that kind of bullshit leads to people being hurt. Or hell, incarcerated. No communication, no play, because there is no consent.
There are lots of "BDSM" relationships which are simply abusive, with a partner being coerced and manipulated into maintaining the relationship. Probably more of them are healthy, but that doesn't change the fact.
Political correctness often urges us to treat all belief systems the same, but all belief systems are not the same. Some of them are inherently prejudiced. People cannot participate in them without being inherently prejudiced. Some of those prejudices are harmful. As a species we are in the process of realizing that women are not inferior to men. Some of us have gotten stuck.