itt no-one can take banter. If it is banter, that is - if they're real friends then they're probably just teasing because they know you won't get too upset and you should just give as good as you get. However if that's not what it is then... I've gotta honestly suggest what LividZephyr said.
Regarding the competitive battling thing - no. You might convince them that it's not all that childish but you'll just earn yourself a reputation as someone who's wayyyyyy too into it and that's opening up a whole new can of worms imo.
This is what I always did back when I played regularly tbh. However I imagine for you it's a bit late for that now so... what I'd suggest is just keep doing it. Next time they try to make fun of you for it and you don't like it, just say "and what?". They only care because you care - if you can show them that you don't care (and if you do care, pretend that you don't lol) then they'll just move on. That's how I approach dealing with anything like this from just petty teasing to full-on bullying and in my experience it's usually worked. *shrug*if your friends are making fun of you for the games you play, then maybe you shouldn't tell them you play it
Regarding the competitive battling thing - no. You might convince them that it's not all that childish but you'll just earn yourself a reputation as someone who's wayyyyyy too into it and that's opening up a whole new can of worms imo.