I've always thought that he was a petty and childish little man, always shouting down the other judges whenever they make any hint of a negative comment about his acts' performances.
Tonight with his screaming and putting his fingers in his ears and yelling at people to shut up, he confirmed it. He needs to control his emotional outbursts (the word "bullying" came from him in the heat of the moment as a comeback) and nasty personal comments.
Don't get me wrong, if he thinks Frankie cannot sing, by all means tell him. Alexandra said the same thing last week but she did it with class and tact, something Louis wouldn't know if it came up and bit him.