Originally Posted by BigZ

Let's say the sun is triangular and green. For the sake of the argument.
That's the whole point - Can prove age discrimination? Go ahead and sue for age discrimination.
Can't? Don't. "That person got the interview because of age/sex/ethnicity/whatever" "No, that person's background is a better fit for what we are looking for".

Exercise in futility.
Not ageism. One candidate spent enough time in the field to gain the basic experience, but probably not enough time to become engrained in doing things a certain way, so is probably more trainable and as such more desirable as a potential candidate. Boom.