Well, what I ended up doing was just quitting for a while. I stopped all Pokemon activity for three or four years (granted, I had only played the TCG for two or three sets, so I'm really talking about video games, which I had played since the day Red came out).
Eventually, I learned that the best way to do it was to just play along with them. Make jokes about how I play it. Not take it too seriously...but making sure that they know that, no matter what they said, I wouldn't stop.
And so, maybe five or six years after I picked the games up again, I started playing with the cards and now, a year later...well, I'm posting on a forum about it.
Ahaha...so if you want my advice, just don't take it so seriously when you're around them. Of course, there's different actions called for by different situations, but that's the best general advice I can offer. The most seriously you take yourself around them, the more they'll mock you or whatnot.
Eventually, you'll find people who you can talk and laugh about this kinda stuff with, so just bear with it for now, y'know?