How do you know? Have you tried it?
If you think that BDSM is not good in real life, then you probably weren't that interested in it, or you had a bad experience with it. Like every sexual kink, you have to be compatible with it and actually do research so you can get the best out of it.
Kinkshaming
I'm just giving those interested the benefit of my own experiences. I'm not about to give out my credentials on this, but if I didn't know what I was talking about, I wouldn't say anything.
I think you're taking it too lightly. It's serious business, and a word of caution is not going to hurt you or anyone else.
Yes
Your experiences might not be the best example. Just because you didn't have a good experience doesn't mean others will. Your comment just seemed so vague that you were saying BDSM is bad as a whole.
People who are turned on by the S&M. A caveat, in RL these things are not going to be anything like the fantasy. Unless you're perverted enough to enjoy things like pain and abuse, I'd advise you to keep it as a fantasy without delving too deeply into it in RL. Doing it in RL will kill your fantasy.