ad hominem

Attacking the person making an argument instead of the argument.

An ad hominem argument rejects a claim because of something about the person who makes it: their character (abusive), or their situation or interests (circumstantial). A fact about a speaker can be a reason to check their evidence more carefully, but it is never by itself a reason to think the claim false.

Examples

"Don't listen to her review of the laptop; she can't even keep her desk tidy."
Not an ad hominem: "He is paid by the company, so let's check his figures against an independent source."