1. Ad Hominem Fallacy

You attacked your opponent’s character or personal traits in an attempt to undermine their argument.

Let’s say you come up with a way make air conditioners work more efficiently and you proposal is shut down due to a character attack such as:

1. But didn’t you use to make fun of science kids when you were young, why should we trust you?

2. But you drive like a maniac, so you must be careless in your ideas as well!

3. You used to work in sales, and people who work in sales are master’s of deception!