Did I make a mistake here?

My flop raise was savaged by the table.

Opponent is a seasoned player who multi-tables. I've seen him make a few loose calls, bu he has a reasonable understanding of the game and he's been ahead every time I've been at a table with him. (As an aside: I don't get why he completed his blind...He had bad position and he had a shit hand.)

PokerStars Game #2214381211: Omaha Pot Limit ($0.10/$0.25) - 2005/07/29 - 10:30:51 (ET)
Table 'Aigyptios' Seat #7 is the button
Seat 1: jj_frap ($24.90 in chips)
Seat 2: Lexx ($4.75 in chips)
Seat 3: terjes ($17.20 in chips)
Seat 4: Fatimo ($14.05 in chips)
Seat 6: HOLLYBUG ($15.65 in chips)
Seat 7: pgrab31 ($12.30 in chips)
Seat 8: sparky41 ($12.40 in chips)
Seat 9: JonnyKid ($21.70 in chips)
PatzeRocks has returned
sparky41: posts small blind $0.10
JonnyKid: posts big blind $0.25
*** HOLE CARDS ***
Dealt to jj_frap [As 8h Ks Kh]
jj_frap: calls $0.25
Lexx: calls $0.25
terjes: folds
Fatimo: calls $0.25
HOLLYBUG: folds
pgrab31: folds
sparky41: calls $0.15
JonnyKid: checks
*** FLOP *** [Ah 2d 3h]
sparky41: checks
JonnyKid: checks
jj_frap: bets $1.20
Lexx: folds
Fatimo: folds
Fatimo leaves the table
sparky41: raises $3.60 to $4.80
JonnyKid: folds
jj_frap: raises $10.80 to $15.60
sparky41: calls $7.35 and is all-in
*** TURN *** [Ah 2d 3h] [Jh]
*** RIVER *** [Ah 2d 3h Jh] [5h]
*** SHOW DOWN ***
sparky41: shows [5d 8d Kc 4s] (a straight, Ace to Five)
jj_frap: shows [As 8h Ks Kh] (a flush, Ace high)
jj_frap collected $24.30 from pot
*** SUMMARY ***
Total pot $25.55 | Rake $1.25
Board [Ah 2d 3h Jh 5h]
Seat 1: jj_frap showed [As 8h Ks Kh] and won ($24.30) with a flush, Ace high
Seat 2: Lexx folded on the Flop
Seat 3: terjes folded before Flop (didn't bet)
Seat 4: Fatimo folded on the Flop
Seat 6: HOLLYBUG folded before Flop (didn't bet)
Seat 7: pgrab31 (button) folded before Flop (didn't bet)
Seat 8: sparky41 (small blind) showed [5d 8d Kc 4s] and lost with a straight, Ace to Five
Seat 9: JonnyKid (big blind) folded on the Flop