This begs the question then, is that person cutting ahead of everyone else "all wonderful?" Because if not, why SHOULD they be allowed to cut ahead of everyone? I mean, I hear a common justification for this type of behavior all the time, "Oh come on, is it really that big of a deal?" Well, if it isn't that big of a deal, just don't do it, and then others wouldn't get upset. If it is a big deal, well then I can understand why you're doing it, but now I think you have to acknowledge why others would get upset.
Isn't it just possible that the kid just really needed to go to the bathroom? Is there really is no patience for a kid to step out of line for that? Come on here. Do you really think it's ok for the whole family to step out of line just so the kid can use the bathroom? Or should the kid just tough it out and try to enjoy the ride? Sure, you can ask him/her to use the bathroom before you get in line, but kids sometimes don't quite get that.
Or maybe it's a case where one person stayed behind to use the bathroom while the others got in line, in that case, then maybe the whole party should've waited, yeah, but when it comes down to it, if 3 people are waiting in line while one uses the bathroom, then the 4th person joins them, is it really going to affect your wait time? I mean, most ride vehicles will take two people anyway, so either you are behind a group of 3 or 4, it doesn't really make a difference.
YES, of course, I know what you are thinking, if EVERYONE did this it would be a problem. But everyone DOESN'T do this. I honestly don't see it happening very often. I think people are getting all worked up over something that isn't NEARLY as big of a deal as it is being made out to be.