Looking in the future is never 100% sure, so I never sell a full stack of an asset. Beside this, when my suspicion is right and the banks are hyping it up, the price could rise again and I can dump another half (of my remaining half) later, and so on and on.
Also when RSK won't deliver their promise or just not get adopted, ETH might have a good future over the longer term and then it is good to own some even if it is controlled by the banks. By owning I will have the power to decide when to dump it, so I don't see it as supporting them.