That's not necessarily true, and that wouldn't be a good reason for them to shoot it down. The Bitcoin market is the only thing in consideration, with Ethereum's market situation being very different. They aren't the same fundamentally either, so they would have to be treated as distinct assets.

A lot of their concerns would also be amplified when applied to Ethereum's, or pretty much every altcoin's market -- they're easier to manipulate because they're smaller, they're more volatile, etc.