Check out this quote on ad hominem attacks. Please read it twice & think about it:
"Serious readers for centuries are alert to recognize that ad hominem attacks generally mask an inability to counter an argument on logical or evidentiary grounds."
It's amazing how many people don't understand this concept or ignore it. Many of these people may have proof of their intelligence, such as having a PhD. Despite this, they don't understand this concept that a smart 6th grader could clearly understand.