Why antagonise the Kuladeivam (family deity)?

Experiences with Maha Periyava: 

A couple had immense bhakti towards Maha Periyava. They would never start anything significant any day without doing puja to his statue. The wife was in the family way, and was in the advanced stage. Not a day passed without them praying to the Sage that the child should be born healthy even though their family deity was Lord Narasimhar!

When the pregnant woman was sleeping one night, Lord Narasimhar appeared in her dream and ordered the couple to name the child after him. The lady argued with the Lord that it was their custom to consult Kanchi Maha Periyava before they did anything. But then Lord Narasimhar was adamant.

The wife narrated the dream to her husband the next morning. They decided to name the child Narasimha and also have a word with the Sage after the child was born. After all, they could not antagonise the family deity!

A handsome male child was born to them. When the initial rituals were over, they went to have darshan of the Sage. They had decided to tell him about the dream and seek his advice.

When their turn for darshan came, they placed the child at the feet of the Sage. Looking at the child, Periyava had a delightful smile on his face. He said to the child, "Generally people name a child only after the due rituals. But then this fellow is born with a name even when he was in the stomach. Isn't that so, Narasimha?"

Even before the couple could think of expressing their predicament, the Sage had already solved their problem! This is how he graces his devotees!