Why to some people claim to like screamo/metalcore, and then hate anything with no singing in it?

here is a copy of someone else's question
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what are some good screamo/hardcore bands similar to "Attack Attack!"
or "The Devil Wears Prada"?
Tired of teh same old bands, trying to spread my variety of bands
around.
Additional Details
NOT LOOKING FOR ANY COMPLETELY SCREAMING THROUGH THE WHOLE SONG. Sorry
but if you listen to that crap, you fail. Gtfo ( :
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I never understood why screaming is good, and singing is good, but
screaming without singing it's terrible and crap and I should be
ashamed of myself and "GTFO" or whatever, that view just seems so,
hypocritical, or silly, I mean sure how about every band just ask you
exactly how much screaming they're allowed to have, I don't get it.