Flush draw all-in

[wahooriver]

I apologize if there are good threads on this subject - have tried searching without success.

3 times in the last 2 days, I have had a strong starting hand, and caught a strong piece on the flop. Opponents have gone all-in with a flush draw (in all these circumstances we have had equivalent stacks). Needless to type, all 3 caught their flushes.

These were not insignificant pushes, but rather major moves.

I do not remember seeing this strategy much in the past. Are other people seeing this frequently? There is obviously no defense.

example

JJ, flop comes Jdiamonds rag spade rag spade
villian goes all-in for around 800 chips (approximately my stack size). I know that I have the best possible hand here, prior to the turn.

I am happy to push here. I was also happy to call - although of course both remaining cards were spades.

Any thoughts - is this a defensible move, or just the tariff for playing against donkeys?