Many typical responses. Mr. X works out, takes his protein shakes religiously, creatine, no2 etc buys flex magazine and attems to follow all the mostly bs workouts in there. Still looks like crap and nothing even remotely like a bodybuilder, much less a pro bodybuilder. So Mr. X starts taking steroids, gets a bit bigger, but still hardly looks like a bodybuilder and nowhere near a pro. Mr. X becomes frustrated and jealous that he can't get anywhere near a decent bodybuilding level, much less a pro level and begins looking for an excuse.
He can't use an eating excuse because that is in his control, he can't use a training excuse because that he is in control of, he refuses to use the genetics excuse because that in his mind is just unacceptable, so he chooses the only excuse left that he can't control. He convinces himself that the pro must take an ungodly amount of steroids HGH etc to look like that. Since Mr. X can't afford 60k of steroids a year like he believes the pro's take, he comes to getbig and decides to start bashing pro's when in reality it is deep seeded jealousy most of the time.
BTW, ones response to steroids is also a part of genetics. Some people grow instantly and immediately from reasonable doses while others can take large doses and get little. Unfair? Yes. However that's life.