It's not okay to put someone one the spot.
Randy is having lunch with coworkers and witnesses one of them lying to another.
Randy wants to find out why his coworker lied to the the other one.
Randy waits to ask his coworker about it later in private.
Randy calls out his coworker in front of all the others.
Randy's coworkers are none the wiser, and they have an enjoyable lunch.
Randy's coworker is extremely embarrassed and his coworkers lose trust in him.