It makes perfect sense - as did the threatened attack on Fort dix.
U.S. located bases have armed gards at the gates - other than that weapons, much less loaded ones, are not carried on base. Weapons are often kept under lock and key.
The terroristic impact of a successful attack on a military base would be huge on the general public. It's a symbolic target, like the WTC, with implictions far more important than the physical damage.
Selfridge ANG base is on Detroit’s doorstep with easy access for islamderthals in the area.