I've been to Texas Stadium, Giants Stadium, RFK Stadium, Veterans Stadium, Candlestick Park, Three River Stadium, and The SuperDome. With the exception of The Superdome in 1994, the crowds at Texas Stadium are not as loud, IMHO. RFK (1989-1994) and Veterans stadiums (1987-1995) were rockin'. Giants Stadium (1983-2001) is always loud. Candlestick (1994) was a tad bit louder than Texas Stadium. But the weird thing is that for some reason you are right about the people who attend games at Texas Stadium not understanding to always be loud when we're on defense and always be quiet when we're on offense.
I laugh when I see fans get louder for Rowdy throwing a friggin' t-shirt in the stands than when we need a stop on defense. I wish I could do 40,000 pregame labotomies to fix it, but I cant.
I can only do what I am physically capable of doing at the stadium and hope the rest takes care of itself.