How can adults be so rude and allow their children to be cruel?

I need to find a happy place to post from but for goodness sake it is January! In Michigan! I have even held off from posting because I have too much whining to do :) So to get this off my chest...
I was talking with one of my friends who son Ben, was also born premature and suffers from CP. Ben is a very bright 7 year old who has come a long way in the short 7 years of his life. They were told he would never walk or even hold his head up, folks this is far from the case. He learned to walk with braces on his legs and a walker. These days he only uses his walker for long distance traveling. Our boys are in the same class and it burns me up and breaks my heart to know that parents do not teach their children how to be nice. Heck, what makes me even angrier is some adults do not even know the meaning of self-control or even manners.
The front seat of the bus...you know, where Ben's adaptive seat is strapped down, and he is strapped in? That is the one. Well the extra spot next to Ben SHOULDN'T BE USED AS THE "IN TROUBLE" SEAT! Ben should not tell his mother that his friend did not get to sit with him because "blank" was in trouble and had to sit there. How is the seat Ben (that is too strapped down in to get in trouble) is sitting in, THE TROUBLE SEAT? Come on folks! Think! That is just rude!
Just in case you did not know, it is not nice for your children to get together and yell "Hey Ben! Bet you're too slow to catch us!" then run away. Stop them! It is mean! In addition, I do not care if Ben is smiling. It still sucks!
Back to the bus (love the bus) when kids say things ranging from "Ben can't get out of his seat" to "Since you can't walk down the steps very well, you should try to fly!" it is not nice. Stop them. Please keep your ears open for what children are saying to other children. It is so wrong that a 7 year old child says things like "I'm just too slow to play", "I guess I'm just not strong", "Mom, I don't think I am strong enough to be seven", "Maybe my legs just have to be crooked", and "I want to go to the hospital so they can fix my brain". These comments are wrong out of anyone’s mouth, let alone a developmentally challenged child.

In the absence of obvious assistance, we face anger. Anger, judgment, exasperation, fear, frustration, impatience, annoyance, and invisibility are words that should never be pressed on a child. As much as I do not, like that, I have to explain the bad behavior of children to my children, I do it because it is what it is, and we can pretend that children know how to deal but that will not make it true. I should not have to explain the bad behavior of adults though. It really makes me wonder if the adults that are so rude were ever taught the meaning of knack and respecting others. OK, that is enough venting for today.