Viable strategy to counter T2 Air rush in current build?

It might just be me, but I feel as if T2 air is just a tad bit unbalanced (e.g. the lack of T2 ground-AA/obsolescence of T1 AA).

I hesitate to call rushing T2 air a 'strategy' per se as I cannot think of real-life counterpart; notwithstanding, many players use this as a sort of debut playstyle, which I personally have nothing against.

Regardless, I find that, unless I myself rush T2 air to overdominate, I struggle against any other players that do. There is, of course, the possibility that I lack the skill, in which case it would be nice to know.

I have tried several strategies to counter T2 air rush -- most of them work ~50% of the time -- but cannot find a solid counter. As an example, given that I last later ingame and haven't been nuked to death, I normally convert a bunch of T1 factories to AA production. However, I cannot seem to find a rigorous and solid counter to T2 air rushing. Any suggestions?

If my radar shows lots of fast-moving air units in their base and if my energy isn't in the red, with my first T2 fabber I'll lay down 3-4 Flak turrets in key points in my base, supported by what T1 AA turrets I built beforehand. Usually stops any T2 air from bothering me.

T1 AA bots are DEADLY against air of all tiers.

Make 3-5 bot factories around 5-6 minutes into the game and just start pumping stingers on infinite build. Have some following you com, some patrolling perimeters around your base. Some mixed in with your land army. You just have to prepare a little early and once you hit t2 some flak cannons also work wonders in combination. I once played a round where my opponent rushed 4 t2 air factories and still had 1 t1 air factory. He had invested so much resources in the factories and assisting them that I just ran all over his base with 9 infernos and way too many stingers XD

There's not much that can effectively counter it.

Stingers are deadly, but they have an extremely small area of coverage and it's easy for gunships to simply go around them.

Flak is pretty helpful, but easily sniped by gunships.

The best surface based defense against air units is the Stingray though. It's INSANE.

The most surefire way to defend against air is to have 1 more Peregrine than your opponent.

The easiest way to counter a t2 Air rush is to:

1) air rush yourself. You set the pace of the game this way
2) If you don't plan to rush, but scout it early enough, switch everything you have to t1 AA and rush a t2 air fac yourself. Make sure your expansions are protected by plenty of AA. Take out their t2 air fac if you can, their assist build power if you can't, and their expansions if you can't do any of those things.

3) Build a t2 vehicle fac NEXT TO their base. Sneaky-like. Short distance for your vanguards to travel. Game over. Next to impossible against a smart/good player.

Anything else you do will lose you the game.

I love sniping enemy advanced factories. Getting rid of your opponent's first advanced factory, especially if you can get rid of it when it is almost complete, or before they get out an advanced fabricator, or snipe the advanced fabbers along with the factory is pretty much a guaranteed win.

As people said before if you scout them and see they're going for T2 air rush just build a bunch of Bot Factories and pump Stingers like there's no tomorrow. If they have just air factories a good bunch of tanks or bots earlier in their base will do a lot of damage if they have stingers enough.
Another good move is go orbital early and try a laser snipe. If they don't see it coming the comm is pretty dead. But build a deepspace radar right after the orbital factory and scout where the comm is first. If you try it and don't succeed at first the next try will fail because he'll build umbrellas and anchors all around the base.