Poker Etiquette

So I am back from my 2 day excursion to Atlantic City this past weekend. Unlike most of you I do not have the luxury of living anywhere close to a casino therefore I have to play online or the rare home game if I am invited or take the 3 1/2 hour roadtrip to A.C. Anyways, I played at the Harrah's nightly tourney last night and the following event occurred and I am still steaming about it.

I was dealt K 10 os in late position and called. Everyone else folded except the Big Bind who checked his option.

Flop: X X J, BB checks and I check.
Turn: K, BB checks I bet 2/3 pot and BB calls.
River: 8, BB checks I bet half the pot (now about 3,000) and the BB calls.

The BB without hesitation says to the effect, " you got it...take it." I show ONE CARD, the KING, because I didn't feel that I needed to show the other card.
I then take the pot but while I am pulling in my chips, this stupid cunt NOT INVOLVED in the hand says, " I want to see his other card." I am then really pissed off because I don't want to show and she wasn't involved in the hand. I ask the dealer and he says I have to show. So stupid cunt got her way.

I realize that I certainly am a very mediocre player but I would never ask to see someone else's card, ESPECIALLY if I am not involved in the hand.

Do I have a right to be pissed? I understand that you CAN ask to see both cards but is it a breach of sportsmanship/etiquette?

BTW, I went on and placed 15th out of 59 players, not making the final table. It was fun though.

So what do youse guys think? Constructive criticism appreciated.