I didn't say that there weren't some people out there who would. However your original post indicated it was a blanket approach of aggression from people who don't have children against people who do.
In Walt Disney's time, no one could probably even imagine an adult pushing a kid out of the way to watch the Mickey Mouse float go by. It just didn't happen. Now, people without kids seem to have some sort of irrational aggressiveness towards people with kids, even in places primarily designed for children. It amazes me when people go to a theme park built for the enjoyment of families and then complain about all the annoying kids. It is not even rational.
In my personal experience, I've had far more parents being very aggressive toward me because their precious child is apparently the most important person in the world and deserves whatever it is they are wanting. I would absolutely stand by ground to see a parade, show, fireworks. Everyone is equal at the parks. I paid my money, like everyone else. If I can help someone else see, then I'll move over, let kids stand in front of me, make space for others. However I won't allow my own view to be blocked, by child or adult. Especially when they arrive a few minutes before and I've been standing there for 30 minutes or more. Yes, I might let a few little ones in front of me, however I'm not going to let 3-4, their mother, their father, their grandparents, their uncles. And yes this actually almost happened to us in October. Apparently letting two kids stand in front of us meant the entire family could push in front too.
I have as much "right" to see anything at WDW as anyone else there, including children. If everyone can see, great. I have and will continue to ask people to move or take their kids off their shoulders when people are blocking us, especially when we arrived first.
Last trip, we watched MSEP and arrived under 10 minutes before it started. We were a few "rows" of people back and didn't complain once about our poor view. It was our fault, we had just walked up at the last minute. If we know we are blocking people, we will try and move over, let people squeeze in. However if people refuse to plan, that isn't my problem. I won't give up my own view for them. We all have to coexist. I do have a problem when people are told they are blocking the view of others (by an iPad, child on the shoulders, pushing forward) and being told "Yeah well I want to see or "Yeah well my kid wants to see." We ALL want to see, that's why we are here!
I'm not suggesting the children are rude, it's their parents. I'm not advocating rudeness, violence or aggression. However, while someones child might be the most precious and important person in the universe to a parent/s, they aren't the centre of the actual universe. I'm sorry but being "5" or whatever age doesn't give you an automatic right over everyone else to see a parade or a show or fireworks. If the parents want to make sure their child can see = plan! People shouldn't turn up 5 minutes before the parade and expect everyone else to make a wide path for them when they have been standing there for, sometimes, an hour or more.
Multiple times just on this simple message board thread there have been responders who have taken aggressive, even threatening stances in order to "defend their right" to see a parade. Stories of kids hands being stepped on and one person advocating a physical confrontation if a child wasn't taken down off of shoulders. And this is while people are in the relative comfort of their own home typing on a message board. How do you think these people would be in the Florida heat, frustrated and angry? Don't pretend that there are not people out there that would push your child over to get something they think they are entitled too. Heck, watch all the videos posted on Black Friday before Christmas. People go absolutely crazy when they feel they may miss out on something they feel entitled too. It's not all as ridiculous as you are trying to make it sound.