It is extremely simplistic to label an ideology such as socialism bad or good, first of there is a distinction between reform socialists and revolutionary socialists, several of the most prosperous countries in the world today have been founded by ideas of the former while the later have had a poor track record.

Secondly there is a distinction between idea an execution, socialism is in idea about equality and cooperation, these are not bad ideas, that being said yes it have often failed in many aspects of execution, first of it often fails to take into account the selfishness of the leaders and more seriously that different industries does not function on the same principles, most seriously the agricultural industy does not mix well with socialist ideas.

Thirdly it fails to actually compare the results produced by socialism with alternative ideas such as capitalism, fascism, feudalism and anarchism, all of which have also cost tens of millions if not hundreds of millions of innocent lives.

Basically socialism isn't bad, humans are.