Childhood indoctrination

[littleendian]

And did I mention that handicapped people are humans and not animals.

That's already at the core of the argument: The sentence above illustrates that we draw a line between humans and animals, but we're exactly talking about whether this line is justified. It's just like white slave traders used to say about the blacks that they were simply born to be slaves, without ever thinking about the underlying assumptions that led them there. If they had they had much sooner seen the fallacy and wouldn't have perpetrated terrible crimes.

As voltair said: Those who can make you believe absurdities can make you commit atrocities.

The ability to suffer and the will to live is the only rational, reasonable criterium for who deserves our moral consideration and who doesn't, everything else is just an absurdity that today makes us commit atrocities. Many animals are today treat in a terrible way while they actually have similar ability to suffer and desire to live as human animals do.