If Bitcoin is private and has to remain private to be fungible but you also want to give the government an incentive not to mess with you then politically you should push for legalizing drugs and then some sort of tax. Perhaps if Silk Road actually gave something back to the Bitcoin community then Silk Road for instance would be more popular and could gain political influence.
If you want to understand why this is a terribly naive idea, imagine Mexican drug cartels sending lobbyists to Washington with boatloads of cash to "gain political influence" in the enforcement of drug legislation on their US-based distribution networks.
Taxes, donations and other stuff like this could take so called dirty money and make it clean by turning something potentially harmful into something potentially helpful for a community.
Dirty money doesn't suddenly become ok because you did something good with it. A pet peeve of mine is when people gloss over the incredible difficulty of applying subjective judgement to broad policy decisions - who decides what is dirty, and who decides what action is "good" enough to ethically launder money?
It's not really about crime and punishment and shouldn't be. It should be about protecting a community and not every community agrees on what should be a crime or on what the punishment should be.
The bitcoin "community" doesn't write or enforce laws, nor should it. There's a protocol that you can participate in or not participate in, and there's people you trust and people you don't. You're right that "not every community agrees on what should be a crime," and again I fail to see how the bitcoin community would agree on what money is "dirty," let alone the much more difficult problem of collecting taxes.
The Bitcoin community is global, it's not located in Washington DC.
...so why are you asking a "global" community to placate the IRS and US government with money?
Bottom line: None of your arguments are specific to bitcoin, this is really an argument about legalizing the illegal. If you replace bitcoin with "cash" and use the same arguments I think you'll see how silly some of these presumptions are. If you want to legalize something specific that's illegal, form a specific group and start lobbying. Asking the entire bitcoin community to pay money to try and make basically everything legal is unrealistic on multiple levels.