Preaching to the choir here, but the phrase is 'preaching to the choir'.

And why would we object to a preacher, if he isn't one like this:

http://redwing.hutman.net/~mreed/warriorshtm/deacon.htm

and is genuinely interested in language? Few engage in the art of rhetoric more frequently.

I exist! I am a pedant! I have a foreboding signature!