Many people vote based on keeping something up because of its importance so that others are sure to see it too and maybe act on it, not just because they "like" or "dislike" what the post says.
I for one, up vote a lot of articles like this one, that I am not necessarily happy about, to help move them up the lists so others are more likely to see them too and perhaps be in a position to help counter it from happening or maybe get motivated by it to start making calls and engage in activism to counter it, etc.
Hell, sometimes I even throw an occasional pity vote to someone that got plastered by down votes just for being honest and discussing an unpopular angle of something.
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