Every leftist political movement of the last century and a half has made similar assumptions (including the National Socialist German Workers’ Party) about its rightness and moral superiority. Everyone of them has brought tragedy to the nation it has governed (misgoverned), usually on a grand scale.
When one leaves behind God-given moral principles, the only thing left is man-made moral principles, which change according to circumstance. The left is, by its very nature, opposed to the very idea of God.
The left’s leaders’ and supporters’ religion is government. Any injustices or inequities is not their responsibility because they vote the right way. They believe they are moral because of the way they vote and they complete a few good deeds such as recycling, buying smaller cars, and/or do not use paper or plastic bags and are not judgmental about many sins. This makes them good people. In their mind god,(if they even think he exists) can’t help but reward them because they are good.