Seems to defy logic. Imagine an employer going through a list of resumes, trying to sort them by gender or race and then picking which pile he/she wants to choose from then saying I didn't discriminate.
I don't think he is saying he didn't discriminate though. He's just allowed to discriminate as employment laws don't cover the court nominations.
Really would be the same as someone saying they would never vote for a woman, black person, muslim etc... You are allowed to choose who you want for whatever reason you want. The president has that same discretion with whatever reason they choose for their nomination.