Although I disagree with BU, I don't think it is an attack on Bitcoin itself. Remember the basic concept of Bitcoin - it's controlled by nobody!
That would depend on a person's point of view. If you look at the hard fork to Bitcoin Unlimited as a collusion of the Chinese miners and ASIC manufacturers and having an allegiance with the BU developers to become the stewards of the network and be the people in control then yes it is an attack on Bitcoin.