You could just as well argue we're all paper-clip maximizers, and simply interpret any evidence to the contrary as short-sighted. The only sense in which you can reduce everything humans do to sex is in the irrelevant and unfalsifiable sense.
That's correct, but why would that reduce trust?
Our brains evolved to make decisions. Yes, they were constrained by a need to survive and reproduce. But those two goals are not the same thing. And the existence of those constraints does not actually preclude any other mode of operation.
You're being absurdly reductive when you conflate any motivation with a need to reproduce.
This is why your argument is nonsense. You're basically trying to define everything as sex. You're playing a silly word game so you can feel smug about this directionless and immature insight.