There is nothing wrong with Bitcoin futures as such. It is more about which method is used for settlement of these contracts upon their expiration or exercise. If Bitcoin futures had been physically settled, that would mean actual bitcoins had to be delivered on expiration or exercise. Then it would be a good thing for Bitcoin. But as these futures are only cash-settled, which means there is no physical delivery, this potentially opens doors to heavy market manipulation provided there is enough trading volume in these futures. The good news is that there is not enough volume to set up any meaningful trap to corner the market in any effective way, so there is no need to worry and ban them.