First off the bat, you'll be pleased to know that police have caught up with two of the lovely specimens who threatened the lady on the bus. Being fans of public transport, I'm sure you've already seen the footage.
Unfortunately, if you've been using public transport recently in the post-PM peak times, you've probably seen stuff like this. Eight hours in the cabin, I know I've seen it. Drunk, aggressive behaviour, usually targeting people who won't fight back (something that real men don't seem to bother with) and being so aggressive that people fear intervening. I've seen it both on and off-duty and the thing that seems to bother me is the fact that these people seem entitled to abuse others openly and without fear of anything. I've stopped my tram before to address passengers similar to these. I've refused to move until they're off. The tough part is that very rarely do I get support from other passengers. I don't blame them though - at least I'm getting paid to do it. However, the sad thing is that if I don't do anything, these people would waste no time complaining.
If stuff happens, coming forward as a witness helps so much, as it has in the bus case. Leaving your details with staff bolsters the case against the offenders. Don't be afraid to call 000 if things look like they might get ugly. I've called on my mobile regarding a vandal scrawling on my tram and the cops appeared right away, no questions asked. If they can turn up to Mr Texta Douchebag's crimespree, don't be afraid to do it. In fact, I encourage it. The only real way to improve safety on PT is to boost those stats that pollies and cops live and die by. Letting this stuff slide is not only condoning it, but it sends a message to Spring St that everything is OK on public transport and no further action is required. Or worse, our stats are down from last year, let's shit-can the PSOs. Not only do we want ferals off public transport, but we also want our public servants to know what happens on buses, trams and trains. If they actually used public transport, this might not be needed as much.
If you're going to report things to the police, vehicles may have to be stopped and doors opened as part of procedure. If things get violent, people have a means to escape and the police have a pin-pointed position to attend. Yes, offenders can escape, but they usually do so on foot. MAKE SURE YOU GET A DESCRIPTION. This includes age, height, clothing, hair, manner, (hell, even if he/she touched off might help). You can supply the vehicle number and notifying the driver that you've called the police would be helpful (as he/she can contact Fleet Operations who can then contact the police - two calls are better than one). It's up to all of us to start fighting back against these social cancers and let them know that we're a decent society that doesn't tolerate racism or threats.
Let me ask you this:
What happens if that girl was you? Being sworn at, abused and threatened. If more people stood up to these bastards, took their photos or video and reported these things to the police, they wouldn't be able to strut around as though the world owes them something. If you were that girl, you would want someone to help you out. Mind you, the person there that needs the most help is the occupant of the pram.