There was originally an argument from Mainline Protestantism* that somewhat bridged the gap from.

Interesting. Do you think it was a sort of convergent evolution or there's actually a traceable line of descent from this bit of Protestant theology to SJWs?

SJWs do commonly carry forward as assumptions ideas like “true” desires aren’t going to be contradictory and therefor don’t need to be put in a hierarchy

Yes, but I read it as, basically, refusal to consider the consequences. It's like you make a list of what you want and pay no attention to the costs or likelihood or even whether things you like are compatible with each other.

SJWs certainly do have utopian tendencies and utopias rarely tolerate close scrutiny.

the cultural value (inherited from Christianity) that we want to increase people’s happiness.

I think this value is deeper and more ancient that Christianity -- it's a consequence of being social animals. If I scratch your back, I make it more probable that you'll scratch mine when I need it. As long at the cost is not high, sure, whatever makes you happy.

But I don't think that's what SJWs are all about.