The same way the Snowden leaks were instrumental into regulation about surveillance, leaks like this are instrumental in crafting better tax policy, so I would say they are a public good. It's also not-quite possible to do it via completely legal means (as vested interest opposition is too big and has too much capital - the only way to battle against them seems to be to do it via not-so-legal means).
So in this case the fight is punching up against people in positions of power, not down onto people that have no power, so I don't see a direct issue with it. If you have power, you should also have the proportionate responsibility.