They realeased their first single in 2000... So? They've been around since '97 or so. And why should I care if you've liked rock since 1996? What does that mean, that you're right about LP being a good band? It means nothing... I could go around talking about how great RATM is, because I'm older than you so I have to be right. See what I mean? It's ridiculous.
Anywho... I can't remember when I got into rock, they weren't the only band, there were other pop rock bands like blink and Green Day, too... But frankly, if you're trying to get into a competition about who's liked rock longer, that's just lame.