Is This an easy Fold?

[octop]

Against passive players Im always on alert when my kings get reriased PF
I rememebr about a month ago I was playing 2/5 nl at the Wynn and had about 1200 infront of me. An agressive player UTG made it 35 to go and I make it 100 straight. All of the sudden a passive calling station (litlerly never raised once ever in 5 hours, but would call call call with any piece) makes it 175 (had me covered) folded back to me and i decide to call. He is very passive post flop, but I knew the board could be 9 10 j q all diamonds and he wouldnt fold to an all in with black aces. However semibluffs were worthless against him. Im am 99% sure he has aces but he wont bet much for me to see all 5 cards but I will stack him if I hit.
Anyway the flop comes 9 10 jack all diamonds (black kings for me)
Check check
Turn black 2
Check call 100
River Check check he tables black aces

Had it been anyone else I played with in 2 weeks in vegas my stack wouldve gone in preflop.