Any effort to hire more people with trait X where X is unrelated to performance on the job will lead to lowering the bar for people with X trait. Once you start

Any effort to hire more people with trait X where X is unrelated to performance on the job will lead to lowering the bar for people with X trait. Once you start hiring disproportionately from the smaller pool then that pool becomes less qualified on average. The more you "look for qualified candidates while not lowering the bar" the more you need to overlook qualified candidates from the other, bigger and more more qualified on average pool. To see it clearly substitute women with race (for example white) and see how immediately racist the policy becomes.