Thank you - was going to point that out myself until I saw you already had.
If you don't trust anything that the Catalyst tells you, then your only option is Refuse, since it's the only course of action that you know for a complete certainty that the Catalyst isn't manipulating. But that's just choosing to fail and let the Reapers win. So you have to place at least some amount of trust that the options it presents are in fact options in order to pick any of them - at which point, arguing that you don't trust, on its own, ceases to be a good reason not to pick any one particular option.
I'd also point out, in response to remarks I saw a couple of people make about how Synthesis somehow validates the Catalyst's argument: no, it doesn't. All it requires is that you believe that the Catalyst is being honest when it explains its motivations. If it is, then picking Synthesis means the Reapers will stop their attacks, because their motivation for them will be gone. You can fully believe that the Catalyst and Reapers are idiots and their arguments are bunk and still decide to take Synthesis, so long as you buy that they actually believe all of that nonsense.