Do we have an obligation to correct non-malicious misgendering?

I put an account on Facebook yesterday of an encounter I had with some random guy. I was dragging a trolley full of boxes to a charity shop. It tipped over as I took it down the ramp. This man came to my rescue, helped me to load some of the boxes back onto the trolley and carried the rest into the shop.

At first encounter, he clearly read me as female, since he addressed me as 'love.' By the time we'd got into the shop (and he'd heard my voice) that had changed to 'mate.' No aggression on his part, and he carried on being just as pleasant, he'd just changed his evaluation of my gender and was addressing me accordingly. Something that happens from time to time, and that I don't always believe has malicious intent.

My spin on this? The guy helped me out. He made a common mistake. I don't think he needs the lesson that no good deed goes unpunished by being corrected (and possibly embarrassed) in front of the shop staff and customers. He'd helped me out, and correcting him would hardly have been an appropriate display of gratitude.

But one of my friends thought otherwise. I am now complicit in every misgendering of a trans person by someone ignorant, by failing to take the opportunity to educate this one individual. I've bascially gone from victim (not that I ever felt like one) to perpetrator, simply by not choosing to make a point. If this guy (or society in general) misgenders someone else, resulting in extreme dysphoria on their part, then I'm apparently at least partly to blame.

I'm just wondering how others might have handled this situation, and whether or not anyone else thinks the friend's assessment is reasonable.