How big a fold would this be?

[Micturition Man]

HU 25/50, 3000 effective stacks.

SB minraises. BB calls with J7o.

Flop is AJ7 with the A and J suited.

BB checks, SB bets 100 into 200, BB raises to 400. SB insta-calls.

Turn is offsuit 4.

BB leads 700 into 1000, SB insta-pushes for the remaining 1800...

This IMO has to be a call against a tough/optimal/balanced opponent.

My question is how often you would fold this against a lesser opponent based on his exploitable tendencies?

Like if you thought the opponent were very nitty and wouldn't minrz AK/AQ preflop would you consider this a pretty easy fold? Or is it more like a huge fold you almost never make?