Yes, Leo spoke out against unregulated capitalism; but No, Leo does did not issue a blanket condemnation of socialism. Rather the "bad" on the left is over-regulated socialism, which in practice tends to be synonymous with dictatorships. And, what do you know, regularly the worst instances of "unregulated capitalism" are also dictatorships. 

Churchill's bon mot is fetching but not fully fair. In Churchill post WW2 world, the choice was seen as between the democratic capitalist West and the dictatorial communist East. More sophisticated reflection today required a distinction between two factors: (1) Mode of governance, with democracy and dictatorship at opposite ends of that spectrum; and (2) Modes of economy, with capitalism and socialism at opposite ends of that spectrum. The the two factors taken together, postulate four fundamental combinations: dictatorial capitalism, dictatorial socialism, democratic capitalism, and democratic socialism.