Although I’m not convinced that sparing spiders is justified on self-interested grounds (aren’t most prey insects less dangerous to have around than spiders? if you introduce new spiders, yes, they will starve, but wouldn’t this still cut the prey population at least in the short term?), you make good points on that front, and more important, you are right that, even if someone’s reasoning is shaky, it is unfounded for me to assume a specific motive without evidence for that motive.
Although I’m not convinced that sparing spiders is justified on self-interested grounds (aren’t most prey insects less dangerous to have around than spiders? if you introduce new spiders, yes, they will starve, but wouldn’t this still cut the prey population at least in the short term?), you make good points on that front, and more important, you are right that, even if someone’s reasoning is shaky, it is unfounded for me to assume a specific motive without evidence for that motive.