I'm a little unclear about something. Do you distrust the Catalyst because you think he's wrong about stuff, or because you think he's lying? These are two very different things, and the case for the first is a lot stronger than the case for the second, which requires some very bizarre beliefs about the Catalyst's actual priorities.
Both. I don't trust the Reaper chief that comes out just when I have the chance to destroy them all and tries to convince me to kill myself. His choice of a child appearance is clearly an attempt of manipulation.
If you distrust the catalyst why would you believe it to pick destroy?
I pick destroy in spite of him, not because I believe him. I see three options, first two require sacrificing myself and hoping for the Reaper chief to be right. One of these options smells of indoctrination (TIM example) the other is something the Reapers are already doing on Earth. Then I see the third option. Catalyst tries to convince me that it is the worst one, all synthetic life in the galaxy will die, I may die because I'm partly synthetic. But this path does not require me to willingly kill myself. If he's lying and nothing will happen - well, at least I've tried and there is no reason to believe he was sincere in the other two cases. If the Reapers are destroyed along with geth and EDI - I've destroyed the Reapers. That's what comes to mind - Stand amongst the ashes of a trillion dead souls and ask the ghosts if honor matters.