The thing is, not all of them do.
I believe the upper echelons of Leftists (the steely-eyed ones interested only in power and domination) understand perfectly that statements like "America's gun obsession is rooted in slavery" are pure, unadulterated pap. These people simply find these absurdities quite useful.
But they are a smaller segment of the Left.
The larger portion of the Left which is composed of both the spittle-lipped ANTIFA cannon-fodder types and the intellectually weak and lazy liberals who cast their votes for Leftists because they don't vote, they emote, actually do believe this idiocy.
And that is unnerving.
There are a lot of very bad,evil people on the left, and not all of them are ignorant tools.
But I would not use the word “unnerving” to describe my reaction to them. What they say is indeed cause for reflection and preparation. But “unnerving” is too much like “frightening” for me.
Sadly, I think they may drive us to the time where it is necessary to “put on the whole armor of God” and deal with them. But I don’t think any real American should feel frightened or unnerved by them.