The most important thing with BDSM is something all vanilla relationships miss out on.
C is for Consent
Every BDSM engagement requires communication, talk, openness and sharing. In fact, folks that practice this usually have a far better relationship then those that don't partake.
As for pain, most people would say WTF. The reality it is all about sensation play and feeling and engaging in consensual power play. This allows women who have been held back and subjugated in life to either take the dominant role and flip the script, or for those alpha women and leaders in life, to embrace their submission fantasies.
Folks that don't understand, miss the big point. Life is about experiencing and growing and sharing, and no matter how good the love making is there is a limited number of positions and if couples privilege is preferred per monogamy standards ... every relationship will go hum drum.
So men can learn respect in the language and tongue of men (not saying that with pride) with a woman taking a man to his knees and learning that the woman is his equal and then some. Pain reinforces this as it "focuses" a person to realize stereotypes and generalizations are wrong.
There are sex acts which have been wrongly stereotyped as homosexual also. E.g. Picture being a woman that loves being taken fully and enjoying that. Does one realize that the man never gets to feel the same level of joy? Why would you want your man to be half a man of feeling the same level of sensations and fullness. Conversely, wouldn't you as a woman desire to step up and see how it would feel to truly take someone?
Imagine taking one another over the edge pushing each other to the limits. Watching your partner struggle against the bonds saying ..... I know you love me, and I believe it .... but will you still love me after you feel this cane? Do note this is not about physical abuse, this is consensually given and taken.
I am a natural switch and a feminist. I am respectful, consensual, and my goal is to make my partner feel safe and loved first.
Then she can get over my lap and and let her alpha liberated woman take a back seat while I turn her backside a lovely shade a red, and trust me ... being a submissive it won't be all about the discomfort as she will be squirming for other reasons too.
The other thing is if this disturbs you, this is ok. It is ok to be vanilla. Just remember I can replace the painful implement with a shaving brush or a feather, and make you understand that pleasure that doesn't stop can be made far more painful then a crop.
I had an ex swearing like a trucker stuck in traffic on the 101, yelling at me to let her free (sexually) but not to untie her. I said "nope" lets edge you one more time.
Be well, live life with love, consent and desire. Closed mindedness is what leads to dead bedroom and deader lives.