It implies that the person is unreliable, deceitful, or untrustworthy. It's a very strong statement of disbelief and lack of confidence.
Here's why:
* The impossibility: You can't physically throw a person very far (especially not if you want them to survive!). This exaggeration highlights how little trust you have in the person.
* The negative connotation: Throwing someone is a violent act, further emphasizing the lack of trust and the negativity associated with the person.
Example: "Don't believe anything that man says, I wouldn't trust him as far as I could throw him."