Reading all the idiotic criticisms and belittlements of Tom Brady and his accomplishments is what drives many Pats fans such as myself to be this obnoxious. (Along with the general jealously spawned hatred of the entire patriots franchise.)
Its extremely difficult to constantly defend the most hated Quarterback in the NFL without losing your marbles.
This is especially true when said slights against him are based off ridiculous double standards and speculations.
Then you take the opportunity to be the bigger man. Any person who knows anything about football knows that Tom Brady is one of the most incredible QBs to ever play the game. So is Peyton Manning. Criticisms and arguments about which of them is better are almost always biased in some shape or form, because the painful truth is you can't make a flawless case for either. Ties drive people NUTS, so they have to keep nitpicking until they find a winner and a loser. Nobody is content with leaving Peyton and Brady as a T-1.
I have to deal with the same kind of crap being a Steelers fan. My quarterback was a well documented douchebag who may or may not have sexually assaulted multiple women up until what, 2 years ago? It doesn't matter how much time passes, I'm always going to have to hear about it. I choose not to get riled up about it because I'm a fan of one of the most successful franchises in NFL history and I have been absolutely SPOILED by their success.
So, do me a favor and try to remember that you are a fan of a team that has attended 6 Super Bowls and won 4 of them in a 14 year span, and that is almost universally considered the Dynasty of the 2000s. Your QB punched his ticket to the Hall of Fame TEN YEARS AGO. Who gives a rat's ass what the hater's think? The worst thing you can do is become one of them.