Say we deploy drones or put more military on the border.
Then what??? Shoot on sight? Don't think so.
Troops are not cops. So, if we deploy them do we do so under the same rules we would use in invading Iraq perhaps?
Sending the military up to the border to shoot civilians may be something WE don't want to do even if a few politicians imagine they can convince us we ought to do.
A static defense system that reacts passively to large crowds is certainly something we need to avoid the use of machineguns and hellfire missiles.