For me, being confident about any decision is the defining factor that will make you most happy with yourself. If you realize how little of a deal a decision to play Pokemon is, even if it is a huge obsession, then there shouldn't be anything offensive about that choice even if people make a big deal about it. The big issue is trying to relate with other kids in middle school, when puberty comes at random times for pretty much everyone. Trying to relate with others when nearly everyone else is trying to figure out if your "balls have dropped" or if you've "become a woman" is a big deal, and hobbies are definately an easy target as something that would define the "old you." I've kinda lost sight about what truly is childish about the game outside of the plot, and the cartoon is still just a cartoon, so it obviously has a target audience. The most appealing thing about Pokemon, to me, is the multiplayer aspect, and that's a great social tool.
The easy thing to say is don't let other people define you. I say "easy" not because it's difficult to listen yourself, but because it's both smart yet dangerous to listen and abide to other people's opinions. The easy way to figure out what is best for yourself is to feel what is right and what is wrong, but don't try to trick yourself. Don't get so carried away with listening to yourself that you become externally deaf, either. Make sure you stay safe, but realize that people want you to be safe and allow you to follow your own path. If you like Pokemon, then that's nothing unusual. That's the whole reason that it's successful, because people like it, so it isn't unusual to like a successful franchise. Basically, doing something independent of your own desires outside of wanting to abide to other people's wills is often not a smart thing to do for your well-being, but make sure you have the insight to know when people want to help you by giving you their opinions. Have confidence, and do what you think is right.
On this topic, I thought of two good essays from the Transcendentialist movement in literature, when people were encouraged to follow their own path. They're very critical of society as there is a lot of bias due to them writing in a time when certain freedoms of speech weren't permitted in America. They do, however, have some timeless insight about the importance of the concept of self. They're good reads for those who like to read, but I still recommend a general understanding of those works for everyone.
Civil Disobedience: http://www.transcendentalists.com/civil_disobedience.htm
Self-Reliance: http://www.emersoncentral.com/selfreliance.htm
I speak from experience, and I hope my insight helps people be more confident with their choice to like Pokemon. Solving bullying is a whole different issue, but being confident and happy with yourself is a deal of its own.
~L_X_F