I know that any player can call clock at any point. My question is, "How long is an acceptable time to consider a decision before a player calls clock?"

In a tournament a player moves all in. One player to act. After about 20-30 seconds the player that went all in calls clock. The player who had clock called on him was pretty upset that it was called that quickly. The all in player said it was his right, then added "I don't want to give any tells." This seemed more like angle shooting to me than strict adherence to the rules.

Opinions???