Age is actually listed as a reasonable mitigating factor under the law, so his admission he would be unable to consider it would make him unqualified.
However, I think he misunderstood the situation. When AF first asked it, she was asking it in the context of "the defendant" who is obviously of the age of majority. I got the impression this person assumes that if someone is of legal age, then age should not be a consideration. I imagine that he would consider age if it was a minor being tried as an adult, simply because he seemed fine with all other mitigating factors. I think he understood the question to read that he would not weigh in more favorably with a younger defendant than an older one simply on the issue of age. But I don't think the factor was communicated well by either AF (on purpose) or HHJP. Too bad, he seemed like someone who would be willing to follow the directions if that was the case and would at least understand all the aspects of it, unlike the other juror y'all have referred to today.
And CM needs to stop using the age and stamina thing. It's one thing to stand up and say it's unfair for the prospective jury pool but the first thing out of his mouth was a complaint about his own ability to work late. Tacky.