Don't call them down - keep folding and when you have a better hand than ace high you call them down and take their stack

Look at it like this, why get your money in when you may be ahead, when you can get it in when you know you are very likely to be ahead? If you call down with ace high whether he has the winning hand or not he'll likely stop being so retarded, even if he is a maniac - even maniacs (unless drunk) pick up on getting called down with Ace high...

So my advice is wait until you have a bigger edge and then exploit it for all it's worth, don't ruin the maniacical tendencies of your villian by calling them down too light