Wow, lots and lots of people ITT that do not have a lot of understanding of poker rules.
Killing a hand is the most severe punishment a floor can make short of a ban. It is only used for the worst violations. Exposing your hand in a multi-way pot with action pending is so far from the "worst" its not even funny. Bad, very bad ruling.
As general rule the only time a hand is killed is when you can not be sure if the hand is valid. E.g. A player mucks his hand into another hand, and now you have 4 cards and can not be sure which two belong to the live hand.
OP I would suggest that point the floor to this site and for him to implement these rules, as they are the root of most poker rooms.
http://www.pokercoach.us/
If this post was in the B&M forum which is where it belongs, you would hear the same thing from the dealers and floor staff that post there, bad ruling, too bad house rules trump, even if they are bad.