Re: I think some people might have missed something...
Why would you spend your budget on "safety equipment" and "fire extinguishers"? Most of them will just sit around for years and never get used!
You do it because a) hopefully you don't want your employees to die and b) even if you don't care, the law requires it anyway.
Equality is primarily about opportunity.
If you never get the opportunity to even see a job advert, how are you going to apply for it?
So yes, it is flat out illegal to filter who sees your job adverts by any of the "protected statuses" - gender, skin colour, age etc.
The only legal question is whether Facebook are also liable for allowing it. Their only plausible defence would be if they have no way of knowing it's a job advert. That seems unlikely, given that "job" is a specific advert category.