Macid, if there's anything I've picked up from making a fool of myself or having parents who hate pretty much everything I say or do, it's that it should never matter what your parents think or say. I know having your own mom think you're weird can hurt but that should never stop you from doing what you want or stop you from being who you are. She is in no place to compare you with the rest of the world and you shouldn't compare youself to anyone else either. You don't need to feel ashamed of yourself because your mom thinks it's weird or bad to do the things you enjoy or take interest in.
Getting this collar represents what you love, dude. There isn't anything you didn't know that your mom didn't know when you got it. You knew you'd be different and perhaps a little strange in other's eyes. That shouldn't hurt. You should feel proud and strong for showing your love for something you like even if others don't understand or look down on it. You took on this challenge the moment you wanted to buy it and you knew it too. Don't prove yourself wrong by getting upset when someone (including your own mother) gives you the WTF look. Wear that collar proud, Macid. I salute you.