How to deal with a condescending manager?

I have recently joined a startup as an APM (My first PM role) and my manager is teaching me the bits and pieces of Product Management. The issue is, while he's helpful and experienced in this field, he sometimes talks to me in a very condescending way which kinda hurts me. I agree that I have a lot to learn and getting a job as an APM is a big thing, especially when you've been in a specialist role for all your life but I still don't get the point of patronizing your juniors. I'm trying to get better at writing documentation and specs but I get very disheartened after every spec review meeting I schedule with my manager.

Any tips for handling this?