Doesn't moot the constitutional and civil-military reasons it's very bad, but the thing that didn't work out like Miller & co. fantasized is the National Guard are relatively less likely to crack skulls and be intimidating thugs, and more likely to hand out dog treats and take selfies with tourists.
I have talked to the local National Guard guys and they're like 'yeah we just stand around all day and say hi to dogs. we have a big trunk of dog treats in the van.'