Does it matter much for piloting? It's quite a mechanical job. I'd argue diversity matters more if you have a team of movie writers (how many movies have terrible female/minority characters because of the diversity problems?) or UX designers, but I don't think your race or gender matters much when piloting a plane...
Of course there is probably currently an excess of white male pilots, but that seems cultural and a socio-economic problem, if you fix the culture (e.g. if little girls also get asked equally as often as little boys if they'd like to be a pilot (instead of a nurse; or if the same percentage of black folks can afford pilot school as white folks), shouldn't this problem fix itself?
Personally I'd cheer on a pilot scholarship for disadvantaged groups, because it'd be nice to see them having some sort of advantage in reaching their dreams after hundreds of years of disadvantages, but I don't think having more black or female pilots would change the job, since, as I said, it's quite a mechanical job. Whereas having a woman or minority in a movie writing crew would probably make a better story due to a more diverse perspective.
Different voices in the boardroom? I'd say a good thing. Different voices in the cockpit? What the hell difference is that going to make, will the plane fly better due to diversity? The pilots are presumably trained to fly the planes as optimally as they can, and their gender or race shouldn't make a difference to the way they operate these machines...
I am not sure how class enters the equation, although it seems to me likely that travelers would prefer to hear neither George Plimpton nor an East-End eelmonger over the intercom.
In the USA, if you want to learn to fly for free, rather than with "enormous debts", it's simple.
All you do is go thru the US Air Force Academy. They take black, white, male, female. They will train you for "free". Yes it requires a service commitment but it's by-and-large a meritocracy.
In the USA you're not entitled to pilot training merely for the sake of "diversity". Pay your dues, earn your way.
I had a cousin who did it. He flew jets for the US Air Force for years. He then became a commercial pilot.