That's a very common tactic for sleazy politicians, and one of the best examples of it actually comes from Biden himself. Go back and look at any of
Biden's Vice Presidential debates and you'll notice that when his opponent asks him a particularly difficult question, he bursts out into laughter. It was
especially bad during the
2012 debate, where he broke out into hysterics almost every time that Paul Ryan spoke to make it seem like what he was talking about was worth mocking, even if he was talking about something
particularly serious.
It's a power play that assholes use because if you're not familiar with the technique, it shames you into feeling like what you just said was so absurd that it doesn't merit a legitimate reply, and that you should be ashamed for even having thought of it in the first place, or to throw you off balance and make you angry because they're laughing at you, because angry people don't debate well. Hillary tried to pull the same trick on Trump during all of their debates, too, but Trump completely ignored it and just kept cutting away at her to throw
her off-balance with shit like, "Because you'd be in jail."
Laughing derisively to dodge questions is a primitive trick but it's
incredibly effective if the person you're dealing with isn't aware of it. Once you're aware of it, it's actually
very difficult to not notice it, and you also start to notice just how often politicians do it.