However I believe they both unquestionably played the river worse than me.

Party Poker 10/20 Hold'em (6 max, 5 handed)

Preflop: Hero is BB with , .
2 folds, Button raises, SB calls, Hero calls.

Flop: (6 SB) , , (3 players)
SB checks, Hero bets, Button calls, SB raises, Hero calls, Button calls.

Turn: (6 BB) (3 players)
SB bets, Hero calls, Button calls.
"
River: (9 BB) (3 players)
SB bets, Hero calls, Button calls.

Final Pot: 12 BB

Results in white below:
SB has Jc Kh (two pair, kings and nines).
Hero has 4d 3d (flush, king high).
Button has Qs Ks (two pair, kings and nines).
Outcome: Hero wins 12 BB.

The bettor afterwards called me a moron. He then said I was "calling and praying." Unfortunately his flop check raise said "I have a King," so the full house possibilities did not seem too serious. His river bet was actually more of a "bet and pray" than my call was a "call and pray." Now does the button really think overcalling here is a good idea!?

You may have been "calling and praying", but you certainly had the odds to be doing so.

You should have told him "what can I say, my prayers get answered once in a while. "

EDIT: Did you consider raising on the river?

It crossed my mind but decided it was chip spewing. In order for it to accomplish anything the button needs to have a 5 or a bigger flush and the SB needs to have just a K. Furthermore, the button needs to fold his 5 and the SB has to call with his K.

yeah, he's the moron for overplaying his hand on a flush and double paired board.

i love it when stupid people think i'm stupid.