The instigators of this thing wisely now SAY it was only a joke. Because inciting a riot to storm "lethal force authorized" property is tantamount to murder.
Their assembly point is said to be 25 miles from Area 51. That's 25 miles of July Nevada desert. It isn't a stroll down a shady lane.
Even if they got there, it does not matter how many begin to enter the area, the first 100 or so to get shot dead will make the rest change their minds right damn now. Make no mistake, such an invasion would be viewed as exactly that. No mercy will be given.
