Why don’t we exploit them when we know it is easy to exploit them?
At the first place, this nature works in that way. By that, I mean strong ones step on weak ones. But our morality and what we have been taught to do in our childhood is to oppose the mindset that we should support and help weak ones. Therefore, when we have managed to give up this code (or morality), we can gain more. Thus the more powerful we become.
Handicapped people, mentally disturbed people, criminal people are burden on the shoulder of society. They mostly do not live happily. (no matter if they live happily, if you ask me) And we are not very happy to see their unhappiness either. This situation should led us to use them, for instance, for scientific experiments.
One more example. Let’s say you are in a class with a stutterer student. He has great deal of struggle to introduce himself and express his opinions. What I have observed in this situation is that people hardly hold themselves back not to laugh. Because they think it is wrong to laugh and that have the possibility to offend him or demoralize him. This “holding back” is very unnatural. By that, I am saying people should release stress and become aware of the fact that they are far more better than the weak stutterer person. They must overwhelm him in the most painful way possible. And our weak friend will suicides and their weak genes does not transfer to new generations. Hence, the amount of weak ones decreases gradually and becomes disappear.
Because every one of us is weak, too: when we are very young, very old, and due to illness or injury (to keep it to the purely physical), sometimes in between unless we’re very, very lucky. Recognizing that we are at times vulnerable, we refrain from exploiting the vulnerability of others in the hope that they will do the same.
Edit: It’s pretty clear from the way you speak about them that you don’t actually know any disabled people. I think you’d be surprised at the full, productive, and happy life you can lead, both individually and as a member of the community, despite a major disability.
A group of weak individuals is always stronger than a single strong individual.
The most powerful and successful societies are those that encourage the weak and the strong to work together for the common good. This means that sometimes the strong should help the weak.
Societies that encourage the strong to dominate the weak can’t compete with more egalitarian societies. “Might makes right” is a crippling philosophy in the long run, because societies that practice it wind up squandering most of their human capital.
There’s the genteel art of flycasting, where the true initiate may actually tie flies stream side in an effort to “match the hatch.” Then there is putting a big ol’ wad of stinky cheese on a hook and using line heavy enough to tether an ocean liner.