I had a similar discussion with my mother last night. Also I used to argue on the job about this stuff. Here's what I think.

Hmm, you're exmo and you're concerned about this? Normally my points are for trying to get TBMs to see reason. So I'll just play devils advocate to a TBM concerned about activism.

Reason number one to be an activist in the church its worked in the past. Even though the leadership will lie about private revelations and it being the right time for the revelation because of changing social views. For example with blacks and the priesthood, it was 100% owing to social pressures to change their ways, were dragged there kicking and screaming and then inevitably they turned around and claim it was their idea, nay gods idea. And that it had to be revealed then.... because people were too wicked to accept that 150 years prior (false and polygamy was not acceptable but they did that anyway).

So to answer your question. when the church makes doctrinal changes doesn't that expose them as a fraud. To many people it does, but the church survived the above level of disaster and seems to have moved away from a bigoted stance. Activists can change the church and so if something is wrong then they should.

Another common argument I get is. "its not the church of /r/baldurthegood, its not even the church of thomas s monson, its the church of jesus christ. and its up to him not us to make the rules. We follow them." The guy who told me that had a very cute, childish level of belief. You can't look at the priesthood and the black example and say that the leadership won't be changed by the laws and attitudes of men and then claim god did it.