How do you really know? Hang out with him 24 hours a day? Nobody knows if anybody else is truly 100% natural. He might be, but you don't know shit.
No, YOU don't know shit. I know Layne well enough to know that it is highly unlikely he has, or would ever, use steroids. Obviously we can never be 100% of most things - you might like wearing your mother's dresses, but I would guess you don't - but he has had numerous blood test and polygraph tests that prove him clean.
Therefore I know more than "shit". I can make a very informed judgement about Layne as I know him. Don't hate and be suspicious because you can't do the things he can.