Before you dismiss anything as trivial, put yourself in the shoes of the person on the receiving end of that behaviour.
What may seem trivial to you, in the abstract, may be damaging to an affected person in their own, particular circumstances.
Let's be clear, discrimination is not improper--discrimination is simply the act of making a choice between different options.
When discrimination becomes improper, is when the choice that is made is not rationally connected to the purpose of the choice. When a person prejudges another person's suitability for a job based on their sex, rather than the objective criteria for the position, that's improper discrimination. When a person has a bias in favour of unmarried employees with no children, that's improper discrimination.
All of these "-ism's" have to be understood in their proper context.
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--James