"Render unto Caesars what is Caesar's and unto God what is God's", even though it might be interpreted as that, I don't really think it's that, and it seems pretty farfetched. Some Christian leftists interpret that as a separation of Church and State, which seems more probable. Even if it's not that political, it's definitively separating worship and spirituality, from political matters, which doesn't specifically prohibit political struggle. Regarding Jesus saying “My kingdom is not of this world", I don't think that's a political statement. His kingdom is not of this world because he doesn't have any royal titles. Yet, he is a "king" because in Christianity he is literally God. And regarding Socialism's rooting in Christianity, the examples you cited are the ones that everyone uses, besides Jesus driving out the merchants from the Temple and Jesus saying that it is easier for a camel to go through the eye of a needle than for a rich man to enter the Kingdom of God. On a sidenote, early Christianity was kinda communist. Engels wrote about that