I have to give props to the OP, cause this is a good topic. I have been thinking about this subject since the first post. I've asked my DW and brother and both say if the child doesn't want to go on, then don't make them. But then I think to my childhood, and my parents used that same thinking and now I'm 25, afraid to go on screaming, ToT, and Splash Mountain as well as a serious phobia of elevators and I think if I had someone to push me I could face my fears. But to truly answer this question you must remember children are just young human beings with different personalities, levels of imagination/fear, and tipping points. Every child is different just like me and everyone else on these forums. While I need to be pushed to face my fears, other can do it on there own or won't at all. Another point is everyone should remember that while we all want to have our very own special moments at DLR/WDW there are thousands of others trying to do the very same thing.
I think I have the hardest time coming up with an answer due to never having an issue with my DD. She got scared while in line for Dumbo right after going on Matterhorn and all it took was picking her up comforting her, then explaining the ride to her, all fixed. But I think there is no true right or wrong for every occurrence of this situation. But I will say everyone in the Halloweenqueens situation was wrong(mostly the parent). While I'm sure she was using an old school mentality of suck it up and thought she was right, she should not have gotten into a shouting match with a CM, and the other guest shouting really should have kept their mouths shut(stuck in line or not). Let the employees handle it and don't escalate the situation. But the act of forcing the child on the ride is still no ones business.
We do not know the child or their situations, the kid could have just been a big sissy who needed a push(Me) but the mom didn't handle it right, and we can truly never know the effects it will have on the kids life;resentment, phobias developed, roller coaster addict or appreciation for parents pushing them. But as a parent I do know everything I do, I do with the intent that it's in the best interests for my kids. And if my kids all of a sudden started freaking out screaming bloody murder as the OP kinda described, I would've at least moved to the side and let people pass by as I would try my best to push my daughter on the ride, whether it be explaining everyone has fears and most we must face or standing at the loading area showing her how happy people are getting off the ride. But dragging is a little much, at least pick up the child.
Sooo, I guess after all that, I would say... is DRAGGING a kicking and screaming child on a ride wrong? Yes. Is making a terrified,crying kid go on a ride they are scared of wrong? Only the parent knows and everyone else should mind their own business.