I have to agree - if you move peasants and disband with another cultures' temples in place it won't help much.

First order of business after repairs is to always rip down other culture temples and replace it with my own +10/+10 temple right away, and upgrade as needed. I want to make happy citizens of my culture asap. Once your temple is in place move peasants in and disband them in the city and they become happy citizens of your culture.

It can be a cheap way to keep the 20K city populations down a bit.