I just joined this new company as Principal level dev and I am building a product service where I need to work with a new graduate who just joined as Program Manager in another team. While we have generally got along well, in the recent few weeks, I have had to push back on design suggestions since they were very localized and don't look at the big picture.
However I have got a lot of pushback from this Junior PM who has strong opinions on anything and does not accept feedback about why something won't work or won't scale. I have even had him challenge my work experience and knowledge and claim that he knows better since he founded two startups when he was in college.
I do not want to pull rank on him since I just joined and I find pulling rank distasteful and a forceful way to establish your dominance but I am at my wits end about how to get him to tone down his arrogance. I have also found his tone is often condescending with regards to how he communicates requirements with often phrases like "Are you sure, you understood that and wrote that down. Can you repeat it to me".
Suggestions on how to get him to tone down his arrogance and overconfidence would be helpful. I would have no hesitation going to his manager and telling him to have his reportee tone it down but having just joined, I don't want to start a fresh war with a Junior.