Will you show me what you have if I fold?

[KenProspero]

Not sure whether this is the right forum, but I'll try it here.

Recently, sitting at a 1/2 nl game at Foxwoods. I had folded pre-flop, so was an observer. MP1 (imo weak player) had raised pf, flop (1 spade) and turn (1 spade). After the turn, MP1 and Button (imo best player at the table) were heads up. When the third spade hit the river, MP1 bet $50 into a pot of about 275-300. This leaves MP1 with about $150 left. Button, says all in (after a normal pause).

After thinking a while, MP1 asks -- "Will you show me what you have if I fold?"

What is the consensus on the correct response and would it depend on whehter button has actually hit the flush?

What actually happened -- Button said nothing and stared. MP1 asked again, Button Stared. MP1 folds. I think this is the best response for anyone who is properly in a 1/2 NL game.