A curtain of darkness is falling upon America and the world

[Just A Box Of Rain]

62. "...the embrace of populism weakens leftist movements....

(because it excludes people) and strengthens rightwing movements (because it excludes people)."

I'd argue it is much worse than that.

As you rightly suggest, Populism is an ideology that requires an "in-group", aka "the people," and an out-group, who are essentially sub-human.

In almost every instance where populist movements take power, those regiemes, which are virtually always lead by demagogic autocrats and totalitarians--as that's the nature of Populism--those in the "out-groups" are subject to attest, imprisonment, torture, and (all to frequently) political mass murder.

Populism has an extremely bloody history as an umbrella ideology. Just look at the death toll of Populist regiemes in the past 100 years or so and consider the lack of respect they have had for human rights, political freedom, and liberal democracy.

In fact, I'd argue that liberal democracy faces no greater threat than that posed by Populism.