The UN Declaration of Human Rights affirms the right to be a member of a trade union, therefore the pilots are perfectly entitled to have one.
What they do with the union is another matter. With global losse running into billions worldwide, now is probably not the best time for unrealistic demands in terms of pay and conditions.
Unions are very much a two edged sword, we've all seen what they've done at General Motors. However I've worked in industries with no union representation and had conditions far below the norm.
I hope their union succeeds and I hope it behaves realistically.