This reminds me of news photography and NOT getting blocked out of a shot. If a person is standing behind 10 or 15 others with cameras and is then somehow surprised that a shooter in the front pops up in the viewfinder, it's a case of not being aware of the realities of the way event shooting works. If you don't want to get boxed out, you need to have taken control and put yourself in a position where YOU are the one who gets the shot. If you want to be in charge of the situation, you'll need to actually "OWN it", and be aware of how human nature works. If you're 25 feet back, and there are four,five, six rows of people in front of you, you were too far back and too timid, or too inexperienced, or not considering of the way events ACTUALLY go down, to have put yourself right up front. It's more a case of being prepared, and anticipating what might happen.
Oh...and I've actually shot news events, press events, sports events, and weddings...I know how it feels to be the person right down in front, blocking the view of everybody, or side-by-side with six to ten other people with cameras right behind a cordon. Again...I bet you saw Uncle Bob there, earlier, right? You wanna stop him? STAND in the aisle, right beside him, and pin him in, in the seats. If he was sitting at an end seat, and experience tells me he probably was, you should have been right there, next to him, so when he stood up, he had nowhere to go except right through your shooting position.