Inter-fraternity rivalries are just part of the sociopolitical landscape of Greek Row. It’s a constant game of one-upping that is essentially a Cold War-style arms race between houses. Obviously, in an environment like that, rivalries are unavoidable. You’re going to have a constant grudge against your competitors. There’s nothing wrong with that while you’re still in school. It’s part of what makes the whole experience fun. But you need to leave it behind when you don your cap and gown and cross that stage.
You’re obviously going to be tight with your brothers after you graduate — tighter than you will be with other folks you meet wherever you choose to live and work once you head off for the real world. If you move to a town full of postgrads (Arlington, Atlanta, Charlotte, and Birmingham come to mind for me), you’re going to encounter other people you went to school with who weren’t in your house. In situations like this, which often occur during bar crawls, concerts, or just backyard parties, you just need to bury the axe. In my opinion, it’s better to unify as alumni of your alma mater then remain divided over old rivalries that none of you even remember the cause of.
When you’re at the bar watching your school’s football team take on a rival’s, you’re not going to care who was a Sigma Chi versus who was a Kappa Alpha. It’s going to be about who’s wearing what colors, cheering for which team, and which school they claim.
Don’t think it’s all lovey-dovey, though. There are situations where old rivalries should be allowed to come back out. Tailgates, Homecoming in particular, are a great example of a time and place where you can let out your hatred for those assholes who lived in the house next door. They had shittier tailgates when you were in school and they throw shittier ones as alumni. There’s nothing wrong with a little friendly shit talking between fellow alumni.
Tailgates and other events back at your alma mater aside, it’s far better to embrace unity as fellow alumni than to keep old fraternity rivalries alive. If you’re in a strange city surrounded by people you don’t know, you’re not going to care that someone was in a different house than you were. It’s going to be about who went to your school and who didn’t. Rivalries like that, like Alabama-Auburn or Carolina-Clemson, are the ones you should care about now. The old ones between houses should remain on campus for the actives to keep alive and for you to relive those few times a year when you return to the battleground that is the Row..