One meta belief I have, is that I think "on the face pursuing idealistic objective A, but actually being tilted toward selfish objective B" is better than "openly pursuing objective B".

Many seem to believe the opposite, typically saying something like "at least the latter is honest".

I feel like what this misses, is that maintaining the face of pursuing idealistic objective A, and using A to coordinate a large coalition, is a pretty big speed bump against attempts to pursue B too brazenly. When "the mask comes off", things actually become much worse, and strategies that pursue B at high costs to other values (including A, and also often general human decency) become unlocked.

Are there any good arguments against this intuition I have? (Whether generalized, or about specific situations)

the problem is that, in order to use this for coordinating large coalition, the people need to believe that at least pursuing the idealistic objective A is a genuine goal rather than just selfish objective B, otherwise it doesn’t work. It comes off as sneaky without the genuineness which people don’t like. 

Convincing the “genuineness” part of pursuing the idealistic objective A is not easy and might not give the speed you are expecting. 

Occasionally you can get away with it but at the cost of credibility