I understand frustration when people don't believe you, that's happened to me on many an occassion.
I've learned to say "you don't think it's me? Okay cool". That's the end of it. I found when I got defensive it made me appear as if I was trying too hard and lying. So, I let those believe what they wish, and I move on.
H*ll, 4 years ago I had haters galore on the Net and I bet they all sh*t their respective pants when they see that I'm still here, better than ever, biz and all.
Take it w/a grain of salt bro, and keep training.
~SC~