So if intelligence is the marker, is it ok to manipulate mentally handicapped people?
We're not talking about marginal intelligence difference. You're making the exception the rule. We're talking different species here. The food chain applies and if you're not at the top there's no advocate built into nature for you. You're a commodity and the only thing securing your survival is your value and the responsibility of the species above you.
There's an analogy to livestock in there if you look hard enough.