I think he defines nice very succinctly. He means people who let their desire to be liked, which he calls affinity, overrule their desire to wield power. It’s

I think he defines nice very succinctly. He means people who let their desire to be liked, which he calls affinity, overrule their desire to wield power. It’s a pretty straightforward values distinction. When confronted with a situation where you have to choose, do you choose the exercise of power over being liked, or do you choose being liked over exercising power? In his formulation nice people tend to choose the latter.