Those guys were charged under the Rail Act for offensive behaviour with at most a $1000 fine.
Normally it is for swearing excessively, drinking or rioting but in this case it's none of these. It's just the presence of them is found to be offensive and that's very much subjective.
It can be whatever we want it to be. Depending on who is in charge it could be used against 50 people wearing the Sourhern Cross, 50 activists going to a climate demo, a men's rights demo or an aboriginal group. All one needs to do is say that they are offended by their presence on a train. Then the police can charge them and arrest them if they refuse to comply.
Just one of things to remind you we are not America with their rights in their constitution.
