I don't like futures for Bitcoin or Ethereum. Because they integrate the current economic system with blockchain. More precisely, they transfer the bad aspects of the current economy to the blockchain economy. Bitcoin is limited. So it is valuable.
NOT like any of us can really do anything about the existence or NON-existence of such products. Right? Good to be aware of these kinds of products to the extent that they might be used to affect, control or manipulate price... or attempted to be used for such.
I think the market manipulation via futures is very overestimated.
Firstly their trading volumes is way less than the one a few big whale can shoot on the market.
Second it is only an historical moment. In the future the liquidity of bitcoin market will be big enough to prevent any unfair use of derivatives (think of fx markets today, where liquidity is so massive basically no one can move the markets).