Müller told it differently when he was asked for it lately in a TV show. He did not say that it happened - he just said it could have happened but if it happened then... It was in a time when they still lost matches and did a lot mistakes on the beginning of the first season (van Gaal totally changed team and system!) - and van Gaal showed the mistakes in his after-match-talks in front of everybody. And he told that he did not show this scenes to ridicule the players just to show everybody what they have to make better. And he did not show his balls to show his superiority or something but to show everybody that he can make himself look stupid, too.
Luca Toni did not speak a lot German then - I doubt he spoke more than 10 words...
For van Gaal discipline is important - and today's Ribery would not have problems with him but the Ribery of 2009/10 had.
Van Gaal did not care about young or old - he just does not care if a player is a star player. It was not only the young ones but it was Ivica Olic, too, who he used a lot in his time at Bayern.
Van Gaal had problems with players that could not take discipline and maybe with some that did not match his system. But he e.g. appreciated when a player took an effort in trying to change - like e.g. Mario Gomez did who after he was not used very often in his first year at Bayern adapted - and in the second year van Gaal adapted the system more to include him as permanent starter.
And he might have had some professionals that did not get around with him (but which longtime manager does not) - but a long list of players that did and really liked him and learned a lot with him.
He made Mourinho from an interpreter to his assistant coach. And I remember an interview with Guardiola in March or April 2010 - short before they got swapped out of he CL - in which he told that he closely watches what van Gaal does with Bayern and the players. That is probably when he started to got attracted of the club and the players.