I think he should go to the PM's boss and to request an in-person meeting to raise the issue. Depending on how big the company is, the CEO may be way too high

I think he should go to the PM's boss and to request an in-person meeting to raise the issue. Depending on how big the company is, the CEO may be way too high up to have any clue about the people he's talking about; he needs to get a read on the situation based on the PM's boss' reaction to figure out his next move.