"And why do people just thinkin, hey it's some kid that wanted to have fun?"
That is a good question. Lets rule out the stereo type idea and go strickly off of what you have posted (that seems fare to me, and gives you the benefit of the doubt).
"I'm a 20yr old who..."
Okay, I've known some mature 20 year olds, and some immature 20 year olds. On average, that still falls into the "kid" range for me.
"most of my peers didn't see it..."
Peer-pressure is a classic sign of someone still being a "kid".
"This is something I do on my spare time. But hey it is fun."
Okay, I think we are seeing where the "fun" part is coming into play.
"I defaced 29 other sites..."
And this at least shows that you like to do it.
"Because i can try to hack there network all the time,..."
I get the same impression as the previous quote.
You seem worried about what people might think of you, but at the same time you seem to missing the signals you're actually sending out. You don't seem to want to be thought of as some kid who is vandalizing other people's proporty, but the actions you took are nothing less (and depending on the other sites, most likely much more). You sound like you would like to be taken seriously for the knowledge and insight that you have, and don't understand why praise for you actions is not forth coming.
Let me give you some advice. First, because you have apologize for this site, I would (if I were you) let the offer to help with security stand. Second, DO NOT contact any of the 29 sites that are commercial sites, they would most likely not wish to hear from you outside of court. Third, offer your services to sites, and then schedule a demonstration with the site admin if they agree (if they don't move on to the next potiential client). And fourth (and most important), find some new "peers" who won't encourage to do things that do you more harm than good.
Remember, you get what you pay for, and all of the preceding advice was free.