Michael, here is one definition of ad hominem:-

"Ad hominem is a general category of fallacies in which a claim or argument is rejected on the basis of some irrelevant fact about the author of, or the person presenting, the claim or argument, as in an attack against the character of person making the claim or his/her circumstances "

When you wrote of Isobel:-

"I find that most of the people who belittle experience are those that don't have any and that belittle advanced degrees are those that don't have any."

... was that not a personal attack, an attack against her circumstances?

Also, and notwithstanding your 'instruction', "And, please, in responding. let's only hear responses that address the post.", do you believe that it would be inappropriate for a person that has no culinary qualifications or experience to judge a meal prepared by a qualified and experienced chef? Or perhaps a patient who has no medical training whatsoever judging the effectiveness of treatment rendered him/her by a doctor?

Cheers