Yes I see it as a concern as well.

And you don't even need a 51% attack.

If bitcoin becomes the basis of a global monetary system block space will become incredibly valuable. Many people predict very high fees. If even a significant percentage (but still less that 51%) censor transactions it will mean that all "unregulated" transactions are competing for even less available uncensored blackspace.

As mining becomes increasingly done less by individuals and more by regulates companies this concern increases.

Trumps statement that "All future bitcoin should be made in the USA" implies an effort to increase the number of blocks mined in the USA which could easily one day come under strict financial regulation. It is not hard to see a future when the US, EU and other nations form treaties agreeing to eachother's bitcoin blacklists/whitelists.

Work needs to be done to ensure bitcoin mining stays decentralised. I like what ocean mining is doing by allowing miners to stay in a mining pool but still choose their own block templates. This goes a long way to ensuring future true decentralization and resisting censorship.