they could have shot the balloon
I think you mean the para-glider, not balloon.
Shooting parachutes usually does not disable them much, but a minigun would likely do it.
The fall would likely be fatal.
And it might have taken out several on the ground. They should have fired when he was still out over the water or the greens, since they no doubt had telescopic sights. I can see why they hesitated, though, since it could have easily been a harmless prank, as it seems in hindsight. But the next one may not be.
Our poor president is going to become a prisoner in the WH, like so many have complained of before. I don't recall even Bush and Reagan having it so bad, although Cindy Sheehan set up an encampment on the road leading to Dubya's ranch.
By air or drone is a new level of dangerous. The SS needs to make an example of the next one.