When do you know you're beat?

[impecunious]

The SB is a maniac playing any two cards and getting lucky to build a big stack. The raise from the BB was just a steal attempt obviously but when I got second pair I thought I was ahead. Knowing he'll play any two do you lay down to the min check-raise? If you don't was I a moran for raising the turn?

PokerStars No-Limit Hold'em Tourney, Big Blind is t3000 (7 handed) converter

Hero (t61515)
UTG (t24270)
MP1 (t24756)
MP2 (t12910)
CO (t84170)
Button (t44871)
SB (t99976)

Preflop: Hero is BB with J[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/club.gif[/img].
<font color="#666666">5 folds</font>, SB completes, <font color="#CC3333">Hero raises to t9000</font>, SB calls t6000.

Flop: (t17400) 8[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets t9000</font>, <font color="#CC3333">SB raises to t18000</font>, Hero calls t9000.

Turn: (t53400) J[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets t21000</font>, <font color="#CC3333">Hero raises to t34365</font>, SB calls t13365.

River: (t122130) Q[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>

Final Pot: t122130