I'm not that good at breathing in

I don’t have thick skin, or, maybe I do, and I can say that’s the reason I’m so droopy around the neck in my middle age.
But figuratively, and by that I mean literally, because when things are said to me, my response is very physical, I don’t manage mean, cruel, nasty, hateful, or mindless behavior from others very well.
The times, besides for the relentless bullying in middle and elementary school, that people, usually strangers, have said awful things to me, or behaved in non-humane ways, are well kept files in my archives.  I visit them when sad, or overwhelmed.  I try and urge myself to not let them get away with it, or say the words that are equally crass, right back to them, because I rarely am at a loss for words.  But, I don’t.  I use my expression, my eyes, and I hold my tongue so that I don’t escalate the situation because ultimately, they are flawed, and I can feel so much better then them by letting them bare it all.  Or wait, no I can’t.   I always end up feeling horrible and stricken.
So, why?  Why do I let it happen. Because, even though I know I’m not deserving of mistreatment, I also know that I’m not going to make them a better person by instructing them, or challenging their base behavior.  I’m only going to have an argument, one that I will win, as I have in the past, and or at least slay them where they stand.  But, no, on that larger scale, I’m not going to make any changes in the person.  Without that, it’s not worth the effort, because my only goal would be to teach something, and I’ve learned, no one likes to be taught, especially, a lesson.