Its all about the whole experience. The experience would be much worse if you had to sit down, hence why I hardly ever watch football on the TV.
Standing up at football is part of the game, if you want to sit there all game like you're at the library then so be it but don't have a pop at people...
I'll go for the stand up option. No point in having the club if you can't enjoy it is there. If I was made to sit down then I'd give up my season ticket. FACT.