You wouldn’t let me bind you if you didn’t trust me.  I wouldn’t do anything to violate that trust.  That’s what BDSM is all about.  

You wouldn’t let me do anything to you if you didn’t trust me to only do what will thoroughly satisfy you.  I wouldn’t do anything I didn’t think would thoroughly satisfy you.  That’s what BDSM is all about!

In this way, at least, BDSM is more “vanilla” than, well, actual non-kink sex!

This isn’t a “no true Scotsman” argument, incidentally, where anything not trusting and being trusted counts as BDSM, and anywhere trust is violated doesn’t.  People fuck up.  It’s just that fucking up isn’t respected, isn’t chortled about, and when we find out about it it tends to get called out instead of shrugged off with a “boys will be boys” excuse.