Principle to Keep

I do not consider myself a principled person. This goes along with the fact that although I consider myself opinionated, I do not have enough support in those opinions to keep them and have them never change. But with principles, I feel like the trivial ones I have don't mean much, and they can be bent in my mind while facing different scenarios. However, there are two that I have that I think will not be bent in any situation, and one of them is very important to me:

Do not make anyone feel significantly small for no reason. If I say something bad to someone, most of the times it is meant as either a joke, or retaliation for that person making me feel like less of a human being. For every action I go through, for every thing I say, there is always an ulterior motive. But in no situation would I be able to call someone a derogatory name, or somehow point out one of their flaws for just no reason at all. Even when I make fun of someone for a joke, or maybe as retaliation for that person "starting it first", I will lie in bed and stare at the ceiling and over think every word I've said, and feel this sickening feeling of guilt.

The reason for that is because many times in my life this has happened to me: people pointing out my flaws, calling me names, for no reason at all. Well of course there was a reason: to make me feel bad about myself, and just because they're bored with their own lives that they feel the need to disrupt mine. But would I do that willingly? Would I want a person to over-think their flaws as they lay and try to sleep? No, I wouldn't. I'm sure that there are definitely some people who don't care about other's opinions of themselves. Everyone says that they don't care, but it makes me feel weak, hearing insults about myself. Of course, I understand the fact that I do not like everybody and that nobody can be liked by everyone and that nobody likes everybody. This is not a principle that I could have everybody live by, not even the people that I really like. But regardless for myself, I do not want to make the people I care about feel weak.