Since I tend to DM a lot more than I game, I never asked the DM to approve any splatbooks. If the campaign focuses on combat, I prefer to run a tank type fighter. In combat, I want to get in there and draw some blood. On the other hand, if the game focuses on role-playing and/or politics, then splatbooks do not matter.
One of the memorable quotes from the Princess Bride is, "My name is Inigo Montoya. You killed my father. Prepare to die." Every group I have played with has always done something nefarious. A pickpocket tries to rob a member of the party. Instead of turning the pickpocket over to the authorities, they practice vigilante justice and execute the pickpocket. Imagine the surprise when a young man ambushes the party and shouts, "You killed my father. Prepare to die!"
The image is based on graphics from here.