CTO gives bad review to everyone

I work at this desi startup, and this other day my CTO invites me to a call in late hours while he was testing a new feature he found some issues in part of the code that an ex employee wrote. I told him I don’t have idea about this specific thing as the ex employee built that out(he was fairly old there and I’m quite new in the company) so I don’t know why he built it that way and if certified functionality exists. Than he started rambling that I’m Sr. Engg here so I should think about things end to end(the ex emp was also Sr.) and said that it was “concerning” that rather than knowing something I answered with I don’t know as he built that part. Some more context - I was given this feature in haphazard manner in small parts and later I become the one who worked majorly on it but the initial setup and some flow of the code was written by the ex emp.

Btw from my colleagues I got to know that he gives bad reviews to mostly everyone and expects everyone to work extra hard though this is the 2nd time he’s given me a concerning review.

What would you do if you were in my case? Should I retaliate by confronting him or let it be because he has a habit of doing this.