The biggest downside is that we will eventually end up reducing the effectiveness of companies and their management because either officially or by 'Twitter pressure' companies will be expected to have "x" amount of women in various positions and will give them those jobs over better qualified men simply to be able to say that they have the right number of women.
OH has seen this in banks already, citing one example where the new female Director of HR had zero experience working in HR, no HR qualifications whatsoever but because they had managed a few branches and "it will look better" she got the job and was making a fairly poor fist of it as a result of not having much idea about what it should actually entail.
I will generously assume all the above is true. In this case, it is almost certain that a better-qualified woman with more experience missed out on the position.
On what base of facts are you making this claim?
The fact there are many many very experienced and very qualified women working in HR.
Except you have no evidence to support your claim? You weren't present at the interviews and didn't see the candidates.
Making comments like you did is just fueling emotion not doing anything to support the argument in either position.