It seems like my oldest son was obsessed for a while. He was also obsessed with locking them first, too! We'd just moved into our first house, and it had weird unlocking mechanisms for the interior doors. I didn't know how to unlock them! He locked himself out of his room during naptime, and wouldn't take a nap on my bed. I thought I'd pull my hair out until I finally figured out how to unlock it from the outside.
I don't know if this would help your particular situation, but there are so many baby-proofing products for doors! If he can't open the doors, maybe he'll stop obsessing. And I also saw a foam thing that fits over the top of your door and keeps it from shutting all the way. It says it's for preventing fingers getting slammed in a door.
My 2 year old is obsessed with cars. I can hardly get him out of ours. I will often unbuckle his car seat harness from the front seat, so he's out and ready when I get around to his door. But now I have to stop that, because he climbs all over the car, and thinks it's great fun to move to a different seat while I'm walking around the car to try to get him! My oldest son loved it, too, but after he pulled Daddy's rear view mirror off the windshield he was banned from playing in the car.