Firstly, do give timely feedback to the person after the candidate. They may not realise and we should always seek to help others to self-improve. Ideally this should be non-judgemental and impact-based. Maybe something along the lines of "Hey there, in that interview when you pressed for an alternative solution it didn't appear you were giving enough consideration to what the candidate had provided. If you alienate a prospective candidate, we damage our brand and don't just lose out on hiring them, we lose out on hiring any smart friends they may have." The idea is not to attribute intent but just to focus on impact. Read up on "non-violent communication" if you want practical pointers on how to do this.
Secondly don't be a jerk but see this as an opportunity to show your character. To quote the Enchiridion of Epictetus:
"Provoked by the sight of a handsome man or a beautiful woman, you will discover within you the contrary power of self-restraint. Faced with pain, you will discover the power of endurance. If you are insulted, you will discover patience. In time, you will grow to be confident that there is not a single impression that you will not have the moral means to tolerate. "
This is something I personally really need to work on (seeing adversity as an opportunity to discover and reinforce resourcefulness within yourself).