If someone rolls a die 10.000 times, and 75% of the time it lands on a six, then instead of "not caring", many people will care. Particularly those that are not betting on the six. Though the people betting on the six have a vested stake in "not caring".
In other words, it's a matter of bias.
If talent is not correlated to race/sex, then we can expect that the number of people of various races/sexes that are represented in the industry should roughly match the general makeup of the population (ie it's a mostly random distribution). Instead we see that this is not case. So either, talent is correlated to race/sex or there is a bias somewhere in the process.
Employer hiring should match the candidate population, not the general population. This is a subtle but very important difference when we also see, for instance, gender bias in graduation rates of STEM fields. (I'm not claiming that this accounts for all bias.) Really, when you say "there is a bias somewhere in the process", it must be remembered that the "process" being spoken of is the entire process that leads to a person being a valid candidate, from schooling to prior experience. (It's hard to get hired as a senior if you can't get hired as a junior first.)
Secondly: there are obviously some differences in the behavior, knowledge, and culture of different groups and it is beneficial for a company to include those and profit from it.
But... you can't have gone through more than 14 years of life without having heard all thread a few times, can you?
See – it feels kinda strange when people willfully misunderstand you and put words in your mouth you never said...
- Race, gender, sexual orientation, disability etc. do not generally affect an individual's skill as an employee
- People from certain groups are under-represented in the industry
- Under-representation generally reflects an underlying problem somewhere, because one would expect various groups to be represented broadly in line with wider society
- One of the problems that can cause under-representation is an existing bias in an industry, which can discourage other members of a group
- One of the approaches to solving this is to help ensure that those groups feel comfortable in the industry
- One of the approaches to helping them feel comfortable is to ensure that communities are inviting, open-minded, and aware that things they say or do may upset or discourage other people, even though they are do not find those things offensive themselves.
It's about observing a trend which seems wrong for various reasons, and attempting to help solve it. I don't doubt for a second that many people go completely overboard on this issue, but outright rejecting any attempt at using, say, gender-neutral language in open-source projects just seems to go completely in the other direction.