[chmod600]

"Valid ad hominem arguments occur in informal logic, where the person making the argument relies on arguments from authority such as testimony, expertise..."

https://en.m.wikipedia.org/wiki/Ad_hominem

It appears that the original comment was valid ad hominem, but still ad hominem.

[parineum]

Any ad hominem cannot inform you about the quality of an argument. It _can_ inform you that you should look at an argument critically but, even in the "valid" form, it doesn't address the argument.