In this case, I think the OS being closed source and kind of a "walled garden" where a company controls everything is what most Linux users dislike about Mac.
None, or at least very few of us hate on FreeBSD or OpenIndiana the way we do on macOSX, so it's not about it being UNIX.
Furthermore, some Linux DEs can resemble the mac interface a bit, like GNOME, or even KDE if it's customized a certain way. Granted, GNOME does have a few haters among us, but not at the same level as Apple.