I have some recent exposure to some beautiful people with damaged souls, and it is just heartbreaking to me. Please read and consider with your own behavior.
*LIES
Lies are the easiest way to destroy someone. This can go either way in a D/s. Trust is essential and lies are the ultimate violation. While even the smallest lie may seem insignificant, it can change a person's perspective on vulnerability and trust.
*BE DISMISIVE OR CRITICAL OF KINKS AND FETISHES
No one expects you to share or even understand other people's fetishes but that doesn't give you the right to be negative toward them. Kink shaming, even with in the community, is all too common, and it can be really damaging, especially if the person is already uncomfortable expressing their kink. Being open with kink is healthy and brave and should not ever be shamed.
*INSENSITIVITY TO LIFESTYLE CHOICES
You have no right to judge another person's choices. I don't care if it is a relationship dynamic, a play style, kink, physical appearance or personal choice, it isn't for you to judge. Recently, I was intentionally guilty of this by mis-gendering a trans person. It was an honest mistake but it clearly had a negative impact on the person.
This list is by no means fully inclusive. It is just a short list of my most recent observations. I welcome others to share additional thoughts on damaging behavior in the comments.