Sure, every mining pool could censor transactions. The question is if miners would use pools that censor because you would not be as profitable.
Also it has nothing to do with 51%. The other 49% are still able to mine blocks, its just less likely.
Discussion
So I guess that's what 'block template" means? the fact that you can modify which to prioritize and which transactions to censor? Regarding the pools, is that what DATUM technology solves? the fact that being in a pool but still able to prioritize transactions you want?
Thats the goal of DATUM as far as I understand it.