participant in a large group activity, not as a spectator at an event.

You don't go to a Metallica concert and sit in your chair. You just don't. You don't go to a Brahms concert and stand. You just don't.

You rarely go to a baseball game and stand. I get that. But you don't go to a serious college football game and spend the game in your seat. Context matters. And if you're too fat, too out of shape, etc., to be able to watch a game standing, you bought tickets in the wrong section. I suggest you make it clear you're looking for tickets in a more sedate section.

Now, every stadium I've ever been to (in particular at Tech), fans have made a real effort to open lines of sight for obviously elderly or disabled people who weren't able to stand for any length of time.

But if someone is just too lazy to stand for a game... find a section that is more sedate. Just a tip: anywhere near a student section probably isn't for you.