My theory is that "leftists" will tend to erect God-like governments in place of God. Since they don't have God to motivate people to altruism and to dispense cosmic justice (to use Thomas Sowell's term), they make the government take on this role, and naturally they give it God-like powers to accomplish its task.
That's a tough one to sell to leftists, many of whom will cease to be rational once the "G" word has been mentioned, not that I blame them. I think the reconciliatory angle may be the most effective with leftists -- i.e. "let's just get along and quit trying to beat each other over the head with the government club." I know this appeals to me, and I think it appeals to most cultural leftists, because I know that on an absolutely fundamental level people want to enjoy other people rather than hate them and react against them.
Interestingly, I would agree that many leftists will seek to make government take on the 'role of altruism' and "dispense cosmic justice." But I don't envision them erecting any kind of government or any thing else for that matter. Leftists tend to bring down, rather than build up.
I do not think a 'lets just get along' strategy will ever work with them. It is my opinion, the only thing that will work with them, is a continual outright confrontation of the statists who manipulate them, right on the leftwing stage itself. But to do that, libertarians will need to take on additional burden. That burden, to use Pete Seager's phrase, is the burden of 'tadegedy and stratics.' Something the right looks up to leadership for, while the left discusses and argues it themselves at the bottom.