Is this Slow-Rolling or am I a Chump?

[W. Deranged]

Random rant. I don't usually complain about anything at the poker table and am usually in very good spirits, but this frustrated me.

To make a long story short, I was playing a hand at Foxwoods 20/40 where I limped in in the cutoff with a small suited connector behind like 5 other limpers. The pot ended up being raised by the button, and we went to the flop 7 handed for a raised pot. I flopped open ended but there was a flush draw on the board. The flop ends up being capped, with all seven players in, two bets go in on the turn without any folds, and on the river I hit a straight that also made a flush possible. My straight was the second nut straight, but after the river was checked all the way to me I found a river value bet. Everyone called.

So, I quickly say "I have a straight but I don't have the diamonds" and expose my hand. No one responds for about five seconds. I start getting really excited thinking I'm about to drag this ridiculous 35 BB pot, and actually stand up and say "I would appreciate it is no one slow rolled me." A few people muck their hands, and about 15-20 seconds pass before a guy on my right turns over his hand, exposing the higher straight (which was a gutshot and frankly I wasn't expecting to see it).

I accused him of slow-rolling and said that that was very poor etiquette. His response was that "he was waiting for someone to show diamonds."

Why is it that everyone is so afraid to expose a loser that they are so inconsiderate of the others at the table.

So, was I justified in my claim this guy was slow-rolling or should I just shut up?

Remember, this was a 35BB pot.

Edit: Clarified that I exposed my hand first.