He didn't hate socialism as it manifests in all socialist contexts. He criticized over egalitarianism including some specific socialist movements of the time. Just like he criticized overly homogenizing capitalism.
Yes, becoming the ubermensch did feed to that criticism in both cases. Extreme socialism levels down competition and crushes the exceptional. The ubermemsch needs the inner struggle. While socialism would also be a struggle in itself to overcone while striving for exceptionalism with its over emphasis on sameness, this struggle is not the type he believes to create the ubermensch. It is the type that creates a person who thinks sameness is a virtue and a goal not to level up beyond. The struggle to him has to be inner not systematically and socially imposed.
His opposition stemmed from what he called " slave morality" which turns the feelings of the noble drive to excell to feelings of guilt. It also stemmed from his views towards individualism and in essence towards comfort and passive existence and lack of introspection and growth which is even present in capitalism today. He called these states of existence the last man.
