I feel I'm probably the most qualified to talk about the altruism of public safety. Keep in mind most people in a public safety profession work a second or even third job in order to support themselves and their families. I would agree that that alone is not an altruistic attitude becuase plenty of people work more then one job in order to do what they love.
As for rushing into a burning building, active crime scene, etc. if they're not trained to handle the situation, they become part of the problem, not part of the solution. Yes it sucks to stand by and watch someone die, but they have families all the same and would like to go home to them at the end of their shift. There is a saying, "You're only a hero when you're dead" and I believe that to be true.
I've done heroic things, but I won't put myself at unnecessary risk to do them. I endanger myself, my crew and the public if I do.
Are firefighters, police officers, etc altruistic? Memorials are full of people who died saving someone elses life. Laying down your life for someone else is probably the most altruistic thing you can do.