I once had a guy actually scream at me that I didn't know what the heck I was talking about to a problem I had him try to solve. That guy didn't get hired.
Yeah. It was amazing to me how long this interviewee went on about how evil it was. Given how big Microsoft is, and how I had nothing to do with what he was mad about, it was somewhat comical how this interviewee couldn't let it go.
Some people make mistakes or talk too much because their nervous but it sounds like your guy needed to get it off his chest.
Interviewees need to be positive and comment positively. You don't need to lie if you don't like a company for whatever reason. Mention it and move on but you never want to focus on that negativity.
Who Knew Running Could Be So Expensive?