Stallman’s insistence that a judge would side with him is pretty arrogant in my opinion; eg looking at Oracle v. Google decades later and how folks deciding the case seemed to be confused about technical matters.

I don't think it was "arrogant" – if you read the link, he explains that he originally thought differently, but he changed his mind based on what his lawyer told him. I don't think you can label a non-lawyer "arrogant" for accepting the legal advice of their own attorney – whether that advice is correct or not can be debated, but it isn't arrogant for someone to trust the correctness of their own lawyer's advice.