If miners pay income tax, could a change in tax laws affect network security? Assuming that more than half of the Bitcoin miners pay taxes on revenue gained, could a increase in income tax laws (or similar) cause those ethical miners to go out of business? ... and the Bitcoin network to be more vulnerable to attack?
Taxes are paid on profits, not revenues. If their mining operation was profitable before, it will remain so even after the tax increase. Also, depending on the kind of tax it could increase equally to any alternative occupation they might have, so there would be no reason it should make any miner operation go out of business; definitely not enough to warrant concerns about the network security.