We know that diverse teams generate better results.
However, as a straight, white, male, I can't know what it's like to go through life as a woman, as an ethnic minority, as a queer person, or someone with a disability (or as a white kid from a council estate, or as a rich, privately educated person, for that matter). The only way to get diversity of life experience within any organisation, the public sector, or community groups, is to include people from these diverse backgrounds. And in a society historically skewed in favour of one type of lifestyle, that will require some form of positive discrimination (at least for now).