Against an average player with neutral table images, easy fold.

But in this case, the guy is clearly an unorthodox maniac. I think you are getting about 2.5:1 pot odds, so it comes down to that gut feeling based on table image on whether you are more than 30% sure he is bluffing.

I think I would probably fold and wait for the inevitable "better situation".
The last thing I would want to see here is for the maniac to take the pot and then leave the table delighted with his huge stack.