Airblast can only do so much. It is really only effective against inexperienced hales.
Airblast feeds hale rage and often hale just rages the pyro and medic once the uber ends. Then he just goes back to hiding. With experienced hales (ex. hales that actually know how to super jump), it's even worse because they just keep running away and hiding.
A good example where camping always occurs is on vsh_rats_office. The teleporter in hale's spawn leads to the room above it, is a typical place where hale just hides in a corner. While airblasting does get him out of there, he can just go back down and go through the teleporter. Rinse and repeat.
Also, pyro is possibly one of the most hated classes in Saxton Hale (cause of airblast). Hales will always single rage a pyro. I swear it's in their genes. It kind of sways people away from the pyro class because of the almost guaranteed single rage and nobody likes to get single raged right?
I feel like it would be obvious when hale is actually camping. To answer your first question, I'll answer the second one. If a portion of the enemy team throws themselves at hale and hale kills them, that's fine. But it's that moment when hale decides to stay there for multiple minutes and it's obvious he won't come out anytime soon is when I'd consider it camping.
For the third question, if the team is in the said space and you're trying to kill them, that wouldn't be camping. But if the team isn't in that space and after a few minutes they don't show up and you refuse to move from that spot, I'd consider that camping.