They're perhaps better said to be energy motivated. And many of them have bills to pay to get that energy in fiat. Or loans to repay. Few really control their own energy production in such a way that if Bitcoin dropped to $0.01 it wouldn't incredibly impact their ability to do what they do, regardless of their ideology. But of course, if it did, chances are, some of us with CPU's wouldn't miss a few cycles here and there to add to the network's hashrate. The question, of course, is whether or not we'd be enough to secure it against attacks. A network that can't defend against double spends, no matter how ideologically pure, is unlikely to hold any value.