OP, based on your description, I have to agree it was really inappropriate and callous for that mom to force her child on that ride. Particularly as he had already done the green option and asked to not go again. My DS has an anxiety disorder. He also, we discovered through daily life, going to smaller carnvials, Ren fairs, etc. loves fast rides, rides that spin, etc. Knowing these things, when at WDW, we slowly worked him up to things we knew he would like if he would just give them chance. Our one unknown, a few years ago, was Space Mountain (there are some knowns - TOT, Mission Space Orange will never happen unless he actually says he wants to do them). We though he would like it, but we were actually unsure. He decided to do it and, though he was scared, there was no panic attack. We went on the whole time I'm thinking to myself, this was a mistake, this was a mistake! Ride ends, we get off, first thing out of his mouth, "That was AWESOME!" It's legend in our family!
That being said, Mission Space Orange is a whole other ballgame. With reports of people feeling sick afterward and really, physically not being able to take it, there is absolutely no way I would do a "let's try it!" on that one.