Is a Unitarian a progressive? I don't know. Frankly, I'm not sure I can reliably identify what a progressive is these days, but it seems clear that in the mind of at least one deranged, "librul" hating, southern trucker, Unitarianism amounts to an evil worthy of mass murder. And while it would be easy to dismiss the actions of the gibberish spouting homicidal maniac who opened fire on a Unitarian congregation in Tennessee as nothing more than a tragically freakish one off, I'm afraid that, from my vantage point, the desperately unhinged character is probably no anomaly. The south, and the great interior of the United States in general is full of people with similarly vicious attitudes as the rampaging, buckshot spraying trucker. And though they almost certainly don't possess the level of malevolence of the aforementioned gunman, don't for a minute think they aren't deeply hostile to liberalism, a doctrine whose hallmarks are expansiveness and inclusion.
It is almost certain that without the advent of liberalism, a creature of The Enlightenment, there would be no United States at all. Absent Enlightenment liberalism, one segment of the British social order of the day, untitled, anglo saxon, male property owners, would not have had cover for their demands for self rule and no model for crafting a system of governance which, at least nominally, enshrined egalitarianism. Over time, more and more members of the U.S. social order, descendants of former slaves, and woman, for example, have been included in the political decision making of the nation, and as a result, one can say that the the initial promise inherent in The Constitution has been, to some substantial degree, fulfilled.
The greatest crisis of liberalism in the nation's history occurred as a result of the issue of slavery, which, of course, by hook and by crook, led to a fraught political environment, insurrection, regional secession and ultimately to a cataclysmic military conflict. The attempted massacre in Tennessee, despite the fact that it came at the hands of someone who was clearly deeply disturbed, might be best viewed as a kind of recrudescence of a very old liberal crisis. With that in mind, It is instructive that a substantial part of the the Tennessee gunmen's rant was directed against gays, a group that is presently engaged in the nation's most notable struggle by a social group to acquire the full compliment of rights, protections, and privileges accorded their straight peers.