You're right. It means: "Rather than [criticizing] a person’s premises or reasoning, one asserts something about the person’s character, ... mental health, like

You're right. It means: "Rather than [criticizing] a person’s premises or reasoning, one asserts something about the person’s character, ... mental health, likes or dislikes." I'm just surprised the first rhetorical tools you decided to use are emotional appeals and being dismissive of anyone who appears like they're remotely not toeing the party line.