Actually, the main reason why the sniper is a problem right now is this:
Yes, as an Ambassador user, getting a headshot from a distance is really frustrating, especially if there's a skilled spy on the opposing team.
But still, there's a big difference between 102 damage and 450 damage.
A sniper can kill everyone with one shot, while a spy needs at least two headshots to kill someone.
I remember when this weapon was in the game, there was a sniper dominating the game and a spy at a distance killing him.
Actually, it was basically a counter-sniper weapon and it was a lot of fun to play.
Think of it like this: there's a big fly, and there are a lot of these flies (fly = sniper).
And a tiny spider can ambush and kill them, but the spider can sometimes bother you too (spider = spy).
So think of it like the predator and prey logic in nature.
The real counter to the sniper is itself. If it's at a distance or in an inaccessible place, the sniper is the real counter.
That's why the Ambassador logic was this:
The sniper is looking somewhere and suddenly a friendly pyro appears... He sees him looking at him from a distance, the sniper is surprised and suddenly BOOM! That's why it's called an anti-sniper weapon.
You might be harassed by the ambassador, but the main purpose of these spies isn't to annoy people, it's to kill the sniper, the biggest threat in the game.