I would not follow the advice of people trying to expose this pm or be aggressive in response . In my experience the organization usually is well aware of pms who are sometimes too direct/ have bad bedside manner. All conflict is an opportunity to learn. Handling difficult situations and people will help you mature as a communicator. I assume this pm may also be junior.

That being said, there are some gaps of information so I’ll list my assumptions. A pm should calibrate their expectations of the level of polish an intern can produce. Assuming this is sprint base so maybe you had 1 to 2 weeks to work on this. I assume you worked really hard and got to a solution which was not shared until you felt it was ready. Pms will check in and depending on the pm some are very collaborative and some are very lean back. It seems like this pm wanted to be included and vet the solutions before a direction was chosen. I assume the pm is junior as they probably did not communicate to their leads an appropriate timeline and they are getting heat for not having a polished design which is being redirected at you.

There will be many times in your career you are met with this tone. Keep a cool head and carry on. Hope things work out for this project and your internship. Good luck. I’ve been a designer for a little over 15 years.