You're making a lot of leaps of logic here, which might be why your colleagues are disagreeing with you. You go from "not everyone can learn algebra or calculus" and "mental disabilities exist" to "therefore intelligence is a scale and controlled by genetics and unalterable," which doesn't really track.
Your previous education, your upbringing, your cultural values, these things all also have huge effects on your aptitudes, and you've just dismissed them out of hand, apparently in favour of pre-determined genetic intelligence. I mean, all I know of you is this comment, so I could easily be missing a lot more context about this argument you've had, but it sounds like you have an axe to grind, not a carefully-considered conclusion.
Your previous education, your upbringing, your cultural values, these things all also have huge effects on your aptitudes, and you've just dismissed them out of hand, apparently in favour of pre-determined genetic intelligence. I mean, all I know of you is this comment, so I could easily be missing a lot more context about this argument you've had, but it sounds like you have an axe to grind, not a carefully-considered conclusion.