Can showing cards in a tournament constitute a call to an all-in?

Question

I faced the following situation today in a Texas Holdem No Limit tournament and would be interested in hearing views on what is correct.

Preflop

Player A shoves all-in. Player B calls. Player C goes all-in or calls (unclear).

Dealer says "showdown" and asks all players to turn over their cards.

Player A turns over his cards, then player B, then player C.

Flop, turn, river

Player A wins. Player C is next best. Player B is weakest.

Player A takes all chips, and dealer then asks Player B to pay the rest to Player C. But Player B disputes this as he only called player A, never an all-in from Player C or anything further. Player B was not asked if he wants to call and assumed Player C's stack was less than his because the dealer proceeded to showdown.

Floor manager is called and rules that because Player B showed his cards, he accepted the all-in from Player C.

Answer 1

A player can not be forced to accept an all in simply by showing his cards.

However, he did not object to participating in the showdown and that means he accepted the all in. He could have refused to participate in the showdown and therefor fold. A player must be very clear if a mistake is taking place and he can not change anything after the next card is dealt. A player is responsible for protecting his action.

Once the next card is dealt all players with live cards have participated, everyone are all in if a showdown takes place before remaining cards are to be dealt.

It was not the event of showing his cards that forced him to go all in, it was the fact that he did not object to participating in the showdown that did. He could easily have refused to participate and mucked. He could have showed his cards, and then mucked them or stated clearly that he folds before any more action was dealt.