In both cases, people would make damn sure not to accept Bitcoins from tainted wallets.
If you have a bitcoin wallet, and I make a tranfer to it, how do you propose to prevent that? If you are a mamber of a mining pool, because you own some minng hardware, as a large number of people are, how do you prevent a payout from that pool if you don't approve of a payment made into it from someone else? Such an action, by your rules, could "poison" the entire network pretty quickly. Most bitcoins originate from mining pools, rather than individuals.
Your proposal signifies a fundamental misunderstanding of what the bitcoin network is, and how it works. The merits or otherwise of bitcoin aside, you are effectively saying that you would not allow transactions between 99.99+% of the network, which is clearly not workable.
Biting the hand that feeds IT
