rabbi of berlin:
I disagree with what you are saying, assuming I understand you correctly.
I don’t believe the proper way to paskin is to look at who you are allowed to argue with and then just take sides as you see fit. It is true that one is not an apikores if he argues with a rishon, but he is a fool.
If Rav Moshe occasionally took sides in a machlokes that was hundreds of years old, I am sure it was with a healthy respect for the hundreds of years worth of commentary which came in between.
I contrast this to a perception I have among some, which is to validate any opinion based on finding a random rishon on which to hang one’s hat. I don’t think that is what any real posek has ever done.
If that is not what we are discussing, then we agree.
(And thank you for the original compliment)