and now women outnumber men in many subject areas including STEM subjects...
We need to remember this 'equity' issue applies to all minority groups. Older people, disabled people, women, there's a long list, but the gist is that such changes could have a positive impact on any of us at any time in our lives and affect any of our family members.
Or we could just leave grad school to the middle classes whose children gain admission through alumni credits and charitable donations. I'm sure someone will complain a few years down the line when Chinese, Indians, Nigerians etc start to dominate universities (they already have an outsize influence) about how they don't have 'real world' skills.
I always refer back to the classic thought experiment (John Rawls), Veil of Ignorance in deciding whether something is just on not. Attempt by society to create equality of opportunity seem perfectly just to me.