River blocking bet gets raised. Call this?

[SABR42]

Villain has LAG stats over small sample. No reads beyond that.

PokerStars No-Limit Hold'em, $2 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

UTG ($207.05)
MP ($150.35)
Hero ($200)
Button ($241.30)
SB ($290.50)
BB ($98.30)

Preflop: Hero is CO with 6[img]/images/graemlins/club.gif[/img], 7[img]/images/graemlins/club.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises to $7</font>, Button calls $7, <font color="#666666">2 folds</font>.

Flop: ($17) 3[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/spade.gif[/img], T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $12</font>, Button calls $12.

Turn: ($41) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, Button checks.

<font color="blue"> I was going for the C/R A/I here. Didn't work.
</font>
River: ($41) 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $20</font>, <font color="#CC3333">Button raises to $70</font>, Hero calls $50.

<font color="blue"> I fire a 1/2 pot blocking bet.

His raise really makes no sense, unless he backdoored a flush. I'm not buying that he has a straight. The only straight draw on the flop is 5-4, and he would have bet the turn with that. He either has a flush or he has air. Thoughts on the call?</font>

Final Pot: $181