There are a lot of folks who are relishing this because many years ago some cool kids decided it was fashionable to hate the Cowboys. Seriously, ask them why they are so anti Dallas. They can't tell you. They just think it's the "cool" thing to do.
49ers and Cowboys have history, dating to the '70s and then the turnaround in the '80s. Bit of it in the '90s too.
The thing that really annoyed me though was their arrogance in declaring themselves "America's team". Sorry, but they are Dallas' team.
After Montana threw the ball in 'The Catch' he was knocked down by one of the Cowboy defenders (not rough or anything, just part of the game) and as the guy was helping Montana back to his feet he said something to the effect of "You just beat America's team."