I think it was suppose to highlight the contradictory nature of Tony. He was always quick to judge and criticize people for their weaknesses/problems, but didn't like to admit his own.

Like when Tony had that big gambling problem. Most of the people around him saw that it was getting out of hand, but Tony refused to do so. In Tony's eyes Christopher's drug addiction was just him being weak minded, while his gambling addiction wasn't a big deal. He didn't like showing any weakness. He was a pretty insecure person. Like when Junior would always bring up how Tony was a bad athlete when he was younger. That would always enrage Tony. He could dish it out, but couldn't take it. He didn't like showing weakness/vulnerability.

Anyway, that's my take on it.