Michigan alum here.  Thank you for letting me post again:

Sooner or later, this will happen to many of us.  Work long enough and you find yourself in a position to labor alongside -- or dare I say, hire -- the enemy.  Congrats on the acquisition, but what do you do about the other issue?  The real issue.  Fine, fine.  No doubt they're talented.  You wouldn't be hiring them if they didn't have talent.  But they come from "there" and ain't no way you're letting that go without some kind of reminder of their unfortunate background.  So, whatcha gonna do about it, bigshot?

The way I look at it, you have three (3) general options.  They go something like this:

1.   You could be professional about it.  A subtle acknowledgement from time to time.  A kind reminder of last year's score (if in your favor).  Invitations to your office -- which has essentially become a shrine to either Woody or Bo, depending.  You leave their birth state out of most discussions and compliment them, when appropriate, on being part of the greatest rivalry anywhere.  But you don't ever cross the professional line.  No comments about arrogant Michigan or inbred Ohio.  No cause for retribution.  It's all about the working relationship.  Except during "The Game" itself.  Obviously not then.  They can eat a d*ck that day.
    
2.   You could go halvsies.  The occasional article via text/email explaining why their team was lucky to win against Rutgers.  How the latest scandal at their school is a clear indication as to the caliber of people one could expect from such a dark, soulless place.  Certainly, you root them on for their professional exploits.  But even during success -- you remind them that it was their boss from the other school who made it possible.  There will be moments where you can extract horrible things from them because they "need" you.  The occasional "Go Blue/Go Bucks" out of gritting teeth in exchange for that extra support which pushes them to victory.  Perhaps the light-hearted practical joke where the next staff meeting is to be held in the den of the enemy -- even when that's not your headquarters.  You love them.  You support them.  But they are scarlet/grey, or maize/blue.  And that's not leaving the front page anytime soon.

   3.  Or lastly, it's war.  Right up to the absolute limits of professionalism.  You don't wanna get in trouble for harassment.  You want them to succeed, of course.  But they're never gonna forget for whom they work.  Off the record bets are common with this strategy.  Particularly ones where the most amount of pain would be the result.  Photos of particularly upsetting moments may appear in public and are usually tied to some larger point about cultural failure and how past success was a mirage, masking an inherent gap in integrity or moral fiber.  The Friday of "The Game" is a holiday when you try to be nice to them, but you can't help hoping for some kind of omen waiting for them at the end of the day -- like a flock of crows sitting on top of their car, so something, No way are you watching the game with this person.  But you have every intention of destroying them on Monday (or calling in sick should you lose).  You do that thing where you whistle in the hallways that week.  And ask questions, like -- where's Rob been?  Who's his team playing in the B1G championship?  I can't seem to find their name on the schedule.

   It's a matter of style, of course.  We all have different sensibilities to such things.  I'm certainly capable of employing any of the three strategies depending on my mood.  But at the end of the day, you want good things for them (alongside yourself), so you gotta figure out which one motivates the best.

   So?  Which is it?