Even though pools are highly centralised, it's a very fragile sort of power and the top dog changes all the time. Once it was slush, then it was deepbit, then it was btc guild, now it's ghash.io ..... if ghash.io started refusing to include transactions for political purposes then undoubtably most miners would abandon them.

 Also did the no-dice policy hurt or help Eligius as a pool? I think these questions are still interesting to explore.

Concerns about pools and how they erode bitcoin security were first raised more than two years ago when Deepbit acquired significant share of bitcoin hash power, but most people agreed that in case a pool would be used for nefarious actions hashers would just point to another more honest pool. The reality didn't match those expectations, Ghash.io was used for double spending. And yet two months after the incident their hashing power share was 15% bigger, and it's only dropped after they stopped accepting new hashers. This is happening because hashers do not care about Bitcoin network security and from that point of view they are evil.