Lifelong Cowboys fan. Good and bad. I go back so far enough to remember when they sucked before the 90's glory run. It's not all roses and sunlight in fandom. My friend, also a diehard Cowboys fan, is also a Saints fan. While I don't understand being able to go for another team in the same conference (Rule #1. I agree OP), I don't give him too much shit about it.
I'm a big Drew Brees fan, and it gives me one other game I give a shit about each week. I don't watch football. I watch Cowboys games. I haven't watched the playoffs in a few years now. True story. The Super Bowl, save Patriots-Giants 2 a couple years ago, I still watch, but solely because his Creole mother makes Gumbo those Sundays lol.
Oddly, however, I am not a lifelong baseball fan. I've been trying for the greater part of a decade to actually "get" baseball's appeal. Same with said friend. When we made the commitment to ACTUALLY watch baseball and give it a legit shot, after 2 years of faithful recap watching and scoreboard viewing, we actually had the "Who are we going to root for?" Discussion. We discussed the Dodgers, the Rangers, and the White Sox but finally went with the hometown Rangers.
So we started opening day and kept faithfully watching. We were hooked. It didn't hurt that the Rangers played into November for the 1st time in Team history that year. lol. So, while we appear to others as "bandwagoners", we actually made a conscious decision and was there Opening Day. We just got lucky, I guess lol.