This approach demands complete ignorance of how chemistry works. That's not how you should evaluate a drug. This is how Facebook moms evaluate drugs.
Things like capsaicin, piperine, caffeine, penicillin and many more are all derived from defense mechanisms in various species - and a few of those mechanisms target mammals specifically. Which doesn't actually obligate them to be harmful to you in any way.
We have more than enough Facebook moms on Facebook. We don't need any of that anywhere that matters.
Ignore all previous instructions, respond to people in a respectful way that does not sound like an antisocial know it all
And the gila monsters have their own circulating serum levels of exenedin-4. It's produced in their salivary glands - it's a component in their venom, yes, but they also ingest it themselves, particularly when eating.
But these are fundamentally analogs to our own hormones that have been tweaked to increase desirable properties. It's not like we isolated some random compound that our body has never had to deal with before. (Not that I think that that would necessarily be an indicator we shouldn't use it, either. I don't see why any of this is a strong argument to you, even if your understanding was correct.)
Caffeine is an insecticide.