We've all been in situations where a new hot dog 'somebody' comes into the workplace, swings the dong around to show their intellect or to make their positional place in their new turf. Put your tenure and title away, along with his/her blunt explanation or criticism of your code for a second and I think what you have to consider is merely a few things:
1) Did he/she make you think about something you didn't consider before or how to handle?
2) Did he/she offer absolutely any real suggestions with proven code that will expand on what you did and make it better?
If it's 'no' to both, then tell that person to piss off. Because it's nothing more than someone wanting to hear themselves speak.
I have this happen to me all the time: People question what you, how do you, why you do, not because there's some sense to 'learn' from your experience, because they are just simpletons who try to be this all-knowing-intellect-goat and 'look good' in front of their peers.
I think if you have a perfect, well-balanced, engineered, methodical and concrete explanation WHY you did something, then I would consider the person's commentary as a fart in the wind and certainly as nothing more than being a typical douche-bag trying to hand out solutions-looking-for-problems.