As an Aussie, I was supportive of Giddy, but if he did knowingly do this, that is pretty bad and I would agree with seeing him kicked out of the NBA or even charged if applicable.
However, if it turns out that she did enter the club on a fake id and that's where he met her thinking she was 18, I feel pretty bloody bad for him. She could easily pass as 18 especially in a dark club based on the photos of Giddy with her, that would be pretty unlucky for Giddy if he gets slung with this because of her deception.