The strongest defense is complete immunity.

Within the design of Bitcoin today we cannot (yet) have the kind true anonymity which would make Bitcoin completely immune to censorship. Instead, Satoshi envisioned a system of pseudonymous addresses (Bitcoin.pdf (section 10: Privacy)) where your non-anonymity was inconsequential because the addresses were meaningless.

Unfortunately, to enact that vision original Bitcoin wallet software needed to use pay-to-ip-address to fetch a new address for every transaction. Pay to IP had issues and so it was largely replaced with addresses. Convenience and ignorance, distractions like vanity addresses caused people to begin constantly reusing addresses. Wallet software was release that made avoiding reuse hard or nearly impossible.  The vision of privacy through pseudonymous addresses has been broken, Bitcoin has lost its privacy. The result is that white/green/black/red/etc listing addresses is not technologically impossible in our ecosystem today.

But, no biggie, we can fix that. Tools like BIP32 let third parties generate fresh, never before used addresses for you without your help, etc.  Of course, this has been possible before, but there was no immediate benefit to fixing your privacy for the bulk of the users— who aren't paranoid enough to worry about their privacy. But to stop the colored lists we need the _default_ behavior of nearly everyone to be behavior that will make those lists ineffective. Only by changing what most users do can we gain immunity.

Thats why I think it's a good step forward that we now have a large mining pool (Eligius) experimentally giving priority to transactions which use never-before-used addresses. Now people who were squishy on the benefits of privacy and immunity to censorship (and the resulting loss of fungiblity) can get a concrete benefit from switching their software or practices to ones which improve everyone's privacy.