The characters upon which the story focuses being a bunch of dbags does not make the white walkers any less evil.
I think you're confusing the characters that we see as part of the story and humanity as a whole in Westeros. Just because we don't see a ton of nice family people with morals and ethics, doesn't mean they don't exist. They just aren't interesting enough to write about.
The white walkers are objectively evil. Most of the main characters that the story focuses upon are shades of grey. The latter does not affect the former.
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