This is definitely within that capacity of humans and could happen. Imagine if Robot armies existed in the 1930s. The Nazis literally set about killing millions of people who they thought weren't beneficial to society. They killed gypsies, Jews, gays, the disabled etc.

Jews were biologically the same as Nazi Germans but it didn't stop them killing them. Poor people become a problem if they're consuming too many resources. The wealth of the rich has to feed and clothe the poor if the poor aren't able to work.

This happened less than a hundred years ago, we haven't evolved since then and as a species are more than capable of doing the same again. Also what happened in the 30's and 40's isn't an anomaly in human history, humans have continually treated one another like this. Look at slavery in the US, apartheid in South Africa, the British empire ruling one 1/5 of the globe. The fact that we have a special word for genocide give a clue about how ubiquitous it's been in our history