In the 60’s the target was just The South, and even stalwarts like George Wallace of Alabama, and Ross Barnett of Mississippi folded. Both were portrayed as a pariah by the rest of the Country, so they stood alone. Also, even unorganized militias would, for the most part, be reluctant to take action against friends and neighbors in the National Guard, who have been “federalized” and believe me, the Feds know this.
Keep in mind that works both ways. The Federal Governments position is much weaker on current issues than it was on Civil Rights in the 60's.
To the contrary, I’d think the Nat’l Guard would be reluctant to ‘vigorously’ enforce this, and side with the ‘unorganized’ militias.