

Pay Attention To The Contrast Between Nick's Facial Reactions Here
I'm sure others have come up with this theory, but I actually believe that - while Nick did end up hustling her in the end - he was actually genuinely touched by Judy standing up for him in the ice cream shop and even felt some remorse for hustling her.
Why do I say this? Simply put, we know that deep inside, he never wanted to be the sly fox society expected him to be. And sure, while Judy definitely overcompensated a bit to make up for the unconscious prejudice toward foxes she had at the time (after all, she did nearly use the spray on Nick just seconds before), the fact remains that she didn't HAVE to stand up for Nick in the first place especially when he was a complete stranger then. She genuinely wanted to do good, and I believe Nick recognized that.
This is the main point of my post here. Pay attention to his facial reaction when she steps in to defend him (provided in the 1st screen shot). He looks taken aback but also touched that someone would actually stand up for him, a fox, of all animals. Now look at his face in the 2nd screen shot. It's subtle, but you can tell that while the reaction he had toward Judy was more genuine, the smile he puts on when facing Jerry (the owner) is clearly part of his mask as he made the vow to never let anyone see that they got to him. He doesn't want Jerry to know how much his comments hurt and so he's using his smile as a shield.
Nick was truly grateful to Judy. However, because of how he grew up, he believed he had no choice but to continue the role of the sly fox with his hustle of her. But even though it was never shown on screen, I truly believe that Nick regretted taking advantage of her kindness and felt some remorse for it.
What do you guys think?