I have no issue with young or old pilots...they both bring different skills to the flightdeck.However some of the younger pilots sometimes think doing a 'good ILS' or whatever means they are great pilots - well you cannot buy experience its as simple as that.It takes years to accure.
Personally I prefer flying with FOs who are of a similar age to me (36) becaue we have more in common - namely kids,wives etc. Maturity is a factor as well.