death note is taking over our friendship....

Liking something isn't ever a problem. That is, unless it goes to something called "obsession".

It's fine and all to talk about some show or something that you like and to have favorito characters, but going completely crazy over it is another. As you've already experienced, it can get annoying. I can't say I know for sure what to suggest, but the only thing I can really tell you is to try getting them to talk about something else. Something that EVERYONE likes to avoid such comments as the "so what" one you mentioned; that statement was rude and a bit out of bounds anyway, and could have been said better.

You and your friend shouldn't even be scared talking to them; anyone can state their opinions. Those who don't listen to them and only take their own are just arrogant, and they definitely won't go very far por listening to themselves all the time. I think that avoiding them, however, helps to some extent. If your other friends are just too stubborn to stop talking about it, and you can't possibly find another way, you need to spend some time with other friends and let it die down. Everything dies down eventually -- as I'm sure you know, nothing lasts forever. Just be patient with your friends and see what you can do for now. If you can even get a little further in getting them to calm down about this, that works too. You're not going to get dramatic results immediately. A lot of things take time.

This is all that I could offer you for right now. Good luck to you, and feel free to ask any other perguntas you may have.