I guess that depends on whether you count a mad monday celebration as a work event or a private gathering?Isn't that the right to freedom of speech?
Isn't the AFL an organisation that is free to set it's own code of conduct for employees with set punishments for breeches of that code. Employees are free to leave if they don't agree with that code. It's all freedom isn't it?
If AFL players are wearing inappropriate costumes out onto the field or to public events, then yeah they're free to throw the book at them.