Assumed political liability.

At the time, sure. With the benefit of hindsight, one of Democrats’ strategic fuckups over the last decade was forgetting that it is one.

I think the Democrat's strategic fuck up is not standing for up for US democracy, always.

Part of that is saying "immigration is good, actually", instead of conceding political positions to the right as they poison our politics.

The Dems should have created a counter-narrative. If you believe in liberal, multi-ethnic democracy, then you must say so. The lesson (that I suppose people have forgotten from history) is that our freedoms (as I am talking about it) must be defended, always, and not taken for granted.