Imagine delegates of views you find actually significantly appealing. (At that level, I think the original post here is correct and your delegates will either use all their caring capacity for helping insects, or insects will be unimportant to them.) Instead of picking one of these delegates, you go with their compromise solution that might look something like, “Ask yourself if you have a comparative advantage at helping insects—If not, stay on the lookout for low-effort ways to help insects and low-effort ways to avoid causing great harm to the cause of helping insects, but otherwise do things that other delegates would prioritize where you have more of a comparative advantage.”
If you view all of morality as “out there” and objective, this approach might seem a bit unsatisfying because—on that view—either insects matter, or they don’t. But if Brian Tomasik is right about consciousness and if morality even as an effective altruist is still quite a lot about finding out “What motivates me to get up in the morning?,” rather than “What’s the one objectively important aim that all effective altruists should pursue?,” then saulius’s point goes through, IMO.
You can have a moral parliament view not just as an approach to moral uncertainty, but also as your approach to undecidedness about what to do in light of all the arguments and appeals you find yourself confronted with. There’s no guarantee that the feeling of undecidedness will go away under ideal conditions for moral reflection, in which case it would probably feel arbitrary and unsatisfying to go with an overall solution that says “insects matter by far the most” or “insects hardly matter at all as a cause area.”
“Marginally for the latter”—that still seems like good news for people who care primarily about animal wellbeing. The way I see it, the environment is not that good a thing anyway (wild animal suffering makes it negative according to my values, and even if others care less about it or care more about aesthetic stuff, surely it moves it quite a lot of the way towards being just neutral), plus there are potentially ways to reverse the effect of greenhouse gas emissions. By contrast, you cannot reverse the direct suffering caused in factory farming.