Do we know what the relative moral worth of cows and insects is?
You assume that this moral worth objectively exists waiting to be discovered and known.
No I don't, it can be subjective and the argument still goes through.
If you comply with the VNM axioms then you have an (effective) utility function and so that moral worth is calculable. And if you don't follow those axioms you get dutch-booked.
I think it's past time for another Stupid Questions thread, so here we go.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Please respect people trying to fix any ignorance they might have, rather than mocking that ignorance.