I didn't say any current atheist supports eugenics. I said if they did, it wouldn't help them establish happiness as a viable goal for everyone, for the reasons I gave.
It's not science or atheism directly that causes economic inequality. It's the ideal of personal liberty. Most Western atheists are secular humanists and liberals, including Sam Harris, who's center-left and supported Hillary Clinton against Bernie Sanders. That makes him a neoliberal, as did his militaristic rhetoric against the Muslim world after 9/11. His Buddhist spirituality is irrelevant, since he wouldn't be in favour of imposing it on a societal basis.