He (Tony G) probably didn't slapped someone when he lost the game. Poker is a war, and in this war people reveal their style of play and character at the table in general. Some are naturally like that or just do it for the game. Tony G has an aggressive and oppressive personality, so he usually tries to manipulate his opponents. This is his way of attacking and need not be hated as every attack has a response as well as a defense as well as a counter attack. He wants to rule his opponents in this way, and always mentally impose his superiority on them. This is so natural and accepted psychology tactic and has nothing near to be called 'disorder' This mentality and attitude is perfectly fine to use in poker because people are fighting for their money on the table.
I passed poker, there are also such people from other fields of games and sports, such as Cristiano Ronaldo. Millions of people like you hate him for excuses just like that (I don't mean you hate it, it's just your reasons are similiar probably). Because, for example, after scoring a goal, he celebrate with a body signs to rival fans meaning to shut up, or he always wants himself to score a goal within the team. He acts selfishly and doesn't seem to care about his teammates, does he? Not like that. That's his mindset, and he could never be a legend if he didn't think so. The reason he got hate is because he was successful.
This is almost the case, for example, when most people lose in a competitive environment, they do not want to accept it mentally and immediately find various unnecessary reasons and try to defame their opponent. When I say competitive environment, you don't have to be a race against him face to face, if you can't stand it even from afar, it means that he is fine and you are defenseless.
It is easy to understand such people, on the contrary, I can't stand people who always show fake smiles and are accepted as good and 'sincere' by the society. So it's not difficult to be funny and have humble attitudes and speeches, but everyone is aware of this role and it is easily done with acting. Taking on this role, I witnessed how uglier most people who are known to the society as good become in certain situations.