I've never been a fan of giving the deck to someone else and making them look like a fool; It's bad etiquette no matter how much of a jerk the heckler is. It just seems like you're trying to beat the heckler at his own game, when his own game is immaturity.
Here are my suggestions:
Firstly, I just tilt the packet down a bit, and if the spectator crouches on the floor I might drop the deck to my side entirely and ask them if they've dropped something, or that "the trick's up here". As long as you don't make it look like you're hiding something, but just being "careless" in not showing the spectator.
Or there are some convincers you can do, some of which are taught on Daryl's Ambitious Card DVD, involving the use of duplicate cards or "lookalike" cards.
Secondlly, the Ambitious Card, while being a great trick and a classic of magic, is ultimately pointless. There is very little point of the card rising through the deck other than "because you want it to". This can make people want to try and catch you out because, in all fairness, you've challenged them by saying "I can do this and you can't - watch!". A solution to this is to pretend that you're not actually doing anything, and it's the card's fault (that is to say the card is heckling you). Provided that you can play it well, and get sufficiently annoyed by you uncooperative card, you should be able to make spectators forget that you are doing sleight of hand, and therefore lessen their want to try and catch you out.
A suggestion for a routine brought to my attention by Derren Brown: Have a spectator select a card and sign it. It is returned into the deck. Another spectator chooses a card sight unseen, which goes face down on the table. You say that unless spectator 2 selected the signed card the trick won't work and you command the signed card to jump to the top. It does. Say that you'll try it with the second card. Place the first card in the centre of the deck, and begin to reach for the second card, wherein you say, "Okay, the current top card is..." - you turn it over and it is the signed card again. That's strange. You put it in the middle so you can concentrate on doing the trick with the second card but every time you turn the top card over to show it as an indifferent card, it's the signed card again! Finally, aftr trying relentlessly to dispose of the card in the middle of the deck, you finally succeed and it doesn't jump to the top of the deck. Relieved that you can continue with the trick, you take spectator 2's card and for the first time turn it over so you can see what it is. It's the signed card!
With a trick with as much drama as that, people will be less concerned about catching you out, because they are enjoying watching you be caught out already. Plus, as you get more annoyed, you can do the move quicker (while still being clear about it) so the audience won't have time to catch you.