No one has really been talking about them in a while, and one guy makes a thread and people go crazy.
I seriously have no idea what the big issue is. Many players and watchers of the game enjoy discussing character placements. No one goes into a tier thread saying, "yes this discussion is going to make my main better", that's what the character forum is for, which I'm sure everyone visits. Also, the discussion gets people's points of view across outside of your own on characters levels, how they face up against other characters, etc, and a lot of times if you're open minded you can learn seeing things from a different perspective. I might have felt a certain way about Raven vs Hawkgirl, but a few months ago i had a great discussion on the matchup in a tier thread that i learned from involving facing HG. Unless of course you're one of those people who thinks they're view is the only view, there are plenty of times you can have good debates and conversations in tier threads.
At the end of the day, people are always going to want to talk about the characters of the game they play. Whether it be after tournaments, because it hasn't been done in a while, or just to start conversation, tiers will be talked about until the game is dead. If you're one of those people that think "o talking about tiers is soooo stupid. I'm too Alpha for that. I discuss tiers 3 years in the game's life minimum. I practice 7 hours a day. That 240 seconds you took writing that post you could be leveling up" then there's a simple solution.
Stay out of the tier lists threads to allow people who enjoy the discussion to, well, discuss and enjoy it, and post in the threads that interest you. Simple as that.