Should I have called this guys 1/5th stack AI with my read?

This guy was terrible. He had already busted out once on a straight draw, and had bought back in. He was making random raises and all ins, as well as calling people to the river with shit. As soon as he bet the flop, I felt I my holdings were better than his, so I raised. Then he went all in...

NL $100 .5/1 Blinds 5 max
undermined is at seat 1 with 197.89
Lowball3456 is at seat 2 with 82.56
sevensUP is at seat 3 with 64.78
tiltmenow is at seat 4 with 98.65
madhatter is at seat 5 with 24.34

Lowball3456 posts the large blind 1.00
undermined posts the small blind 0.50

undermined: Kh, Qs
LowBall3456: --, --
sevensUP: --, --
tiltmenow: --, --
madhatter: --, --

Pre-flop:

sevensUP: Fold
tiltmenow: Fold
madhatter: Call 1.00
undermined: Call 0.50
Lowball3456: Check

Flop (Board: Ad, 2c, Ac):

undermined: Check
Lowball3456: Check
madhatter: Bet 1.00
undermined: Raise 5.00
Lowball3456: Fold
madhatter: Raise 22.34
undermined: Call 18.34

Turn (Board: Ad, 2c, Ac, 7d)
<Players are All in>

River (Board: Ad, 2c, Ac, 7d, 4s)
<Players are All in>

Showdown:
madhatter shows (9h, Tc), A pair of aces (Ad, Ac, Tc, 9h, 7d)
undermined shows (Kh, Qs), A pair of aces (Ad, Ac, Kh, Qs, 7d)
undermined wins 47.68 with A pair of aces, King kicker.

Can I make calls like this with nothing? Or should I just fold in situations like this even though I think I might be ahead? I think how the situation would have been different if he had pushed for $40, or $80 or $100. I probably couldn't have called then, no matter how solid my read...right?

I'd make that call. Ballsy - good for you.