Of the world's over 7 billion people, how many can today afford or even practically buy bitcoins? Not many percentage wise. And someone said that 70% of the U.S. population today don't even know what bitcoin is.
So how is that fair? It isn't. Because the opportunity to buy early is very lopsidedly distributed in society.
What's wrong with that? Neither can everyone have a Porsche. But everyone is free to buy it, they just need to give goods or services in exchange.
The only difference is that Porsche is a consumption asset. If a majority of the people have to do without Porsches, it would be considered acceptable. In the scenario that Bitcoin becomes the de-facto currency of the world, excluding a large part of the world from holding bitcoins (because they are priced out) may be considered unfair.