Everybody has problems, the sane person deals with them in a way that works for them.
I always want to know about a sub’s previous problems with abuse so that I can avoid things that would upset her. I know of one sub that enjoyed rough sex but had an absolute limit of face slapping. Why? Because a previous bf had slapped her in anger, so she always associated slapping with anger and abuse. I am sure that if she had found BDSM first she would have accepted face slapping as easily as she did hair pulling and flogging.
Statistics show that abused people end up in BDSM because a significant number of people who are abused actually choose the personality type that likes to control them. The problem is not simply that people are abused, but that many subs are turned off the BDSM lifestyle because of cultural misconceptions.
Abuse is always wrong, as any but an abuser would agree with. But BDSM is not about abuse, it is about consent. If you do not understand this, why are you here?