Imagine if every flower were the same shape, colour and size. We would crave difference, diversity and interest.
Why then do we marginalise and judge difference within our own human kind?
Our judgement/lack of acceptance of others is simply a reflection of our own mind and the degree of separation and worth we feel inwardly.
When we are unconscious to this in ourselves; to varying degrees denying it, then we have to put it some somewhere and so we project it outwardly.
When unkindness is present, it has nothing to do with the object we are judging/marginalising. It has everything to do with the mind perceiving and enacting it that way.