If anything, I personally feel embarrassed when someone finds a bug in my code / system. Especially if it's a simple bug.
Mistakes happen, no programmer is perfect.
If their tone was off just this once, I'd brush it off. People have bad days; you never know what someone is dealing with outside of work. If their constantly being mean about something, then address that separately and try to find out why. You may find out someone is having a hard time and could use your help / guidance / friendship.