I fundamentally disagree with the idea that it's a virtue to act politely and "professionally" in all circumstances, no matter what the provocation. I think it can be entirely reasonable (depending on specific circumstances) to publicly shame someone who has been publicly acting like an asshole.

Simply being wrong in public deserves a gentle correction (possibly in private, again, depending on the circumstances), but often I don't really care to be nice to people who aren't being nice. It's certainly possible that being nice all the time in situations like this gets you better outcomes overall, but we all have a limited amount of patience to dole out, and some people just don't deserve it sometimes.

And on the other hand, some people don't get the message when you respond politely. Responding politely in this case could just as easily teach the junior that his debugging strategy (blame anyone but himself) and dickish tone were completely ok. There's certainly a polite way to inform the junior that his behavior won't be tolerated, but I can't fault someone for simply responding in kind.