The judgement is entirely subjective and without a legal system to fall back on it really comes down to conjecture, so it's ultimately a bit of both. Offering a bagel instead of cash is a kind gesture and if he wanted to hold on to the bagel the homeless guy wanted maybe he should have specified that on the front end but he also had no obligation to turn over a bagel in the first place so who's to say there's anything wrong with him changing his mind and refusing to make that singular bagel available?