Most reports indicate militia to be "right wing extremists" and often "zealous" (religious).
That is not to say every group will act. They seem to get a lot out of play-acting, running around in camo & face paint, etc.
But, there are always those who are perhaps already a little on the edge, and take the increased rhetoric to heart.
And just so there is no confusion, NO I do not think every Republican is a militia member or zealot. I simply think that particular branch of the party has been most vocal in the last 3+ years.