Ad Hominem (Personal Attack)

(1) William Dembski argues that modern biology supports the idea that there is an intelligent designer who created life.
(2) Dembski would say that because he’s religious. Therefore:(3) Modern biology doesn’t support intelligent design.

This argument rejects the view that intelligent design is supported by modern science based on a remark about the person advancing the view, not by engaging with modern biology. It ignores the argument, focusing only on the arguer; it is therefore a fallacious argument ad hominem.

Ad Hominem arguments attack the source of an argument - not anything within the argument itself.

Here is another ad hominem arguement:
The WTC towers collapsed at freefall velocity and therefore it must have been a controlled demolition.
Rebuttal:
Experts say the WTC towers did not collapse at freefall, and this person is not an expert on Controlled Demolition or physics, therefore the towers did not collapse due to Controlled Demolition.