People who can't sympathize with Peter's situation don't understand how much Jennies death affected him. Peter's reason to take revenge on Philip may seem dumb, but this is his only way he knows how to "avenge" Jennie. Peter feels responsibile for her death because he didn't believe her at the time ( plus Jennie pinning the blame on him in her suicide note) therefore hes putting all this effort to ruin woo yeons reputation. Even after he found Philip's "weakness", Peter was still conflicted on what to do. He has suppressed his feelings for Philip because he didn't want to betray Jennie. I don't see any reason in hating on Peter as he is also a character with flaws, just like Philip.
hai