A "morality pill?"

Peter Singer, the famous ethical philosopher, writes in the NYT (with one of his researchers):

If continuing brain research does in fact show biochemical differences between the brains of those who help others and the brains of those who do not, could this lead to a “morality pill” — a drug that makes us more likely to help? Given the many other studies linking biochemical conditions to mood and behavior, and the proliferation of drugs to modify them that have followed, the idea is not far-fetched. If so, would people choose to take it?

Or would it be a dystopia without free will?