One is bias: take, for example, the archetypal example of orchestra musicians sampling their work behind a curtain so directors can be less unfair when hiring: gender distributions have indeed significantly shifted, because we've removed gender out of view for a critical moment. This, of course, doesn't work if said director is a raging misogynist who will scream "no! no women!" when the curtain reveals the looks of whom he had approved.
The other is underrepresentation. This takes as a given that {women, racial minorities, the mentally ill...} should be represented in important positions in rough proportion to their general share of the population. Now, there are reasons to support this in some cases: preventing that injustices from one generation pass on to the next, for example, or ensuring that the unique contribution that epileptic cyclops can give to the world of cinema. But:
-- not everyone that's in opposition to bias is also in opposition to underrepresentation per se. It's just dishonest to mix the two; particularly in tech circles that have had a long, there's-one-right-answer culture that might not be perceived as benefiting from increased diversity at all. There's also the wider issue of whether diversity should be means to an end or an end unto itself.
(I mean, these are positions that exist. What bothers me is the Trojan horse mechanics at play; it predisposes me against one side when I really haven't thought enough about the subject to have a proper opinion.)