My own personal point of view is that - ok - all of the tracks in a production have to be great if you want a great final product. Arranging, songwriting first, then tracking, then mixing, then finally mastering.
If you think "great songwriting" you'll probably have a good rhythm section foundation (drums and bass), a great guitar harmony, riffs and parts and a cool, expressive, intense vocal melodic line.
Now..think keyboards..you have to ram them into a great songwriting..it's easy to think why they get hated so much: because 1) it's easier to screw up a great songwriting than to add something to it (whatever you're adding to it, be it keyboards or whatever else) than to improve it and 2) adding stuff over stuff makes it harder to keep things simple and effective.
So bottom line is, keyboard lines might often be things you add at a later time or get less "priority" in the band than the strong kick+snare+bass+guitar riff and vocal line thing. So anything stupid, lame, useless, etc. MUST BE HATED
with all your heart.
..but if you add something MORE to even an already-great songwriting, keyboards are LOVED, instead of hated..because they add so much three-dimensional stuff to the arrange.
It's not about hatred or useless xenophobia..
it's more about ..you have to hate stuff that is added by the pound and gives nothing to music..keyboardists tend to be that way.
Ssscrew them! *and I am a keyboardist*
PS: I know my examples starts from thinking keyboards are not the foundation of a great songwriting..they can be, they often are, too...but if I took some song or arranging where keyboards are the foundation..I doubt they'll get hated..so for the sake of the topic..I just took a very frequent situation, since we're talking about metal keyboards..I assumed BIG GUITAR SOUND >)