Whatever. If the 4 year old wants to preach, he wants to preach. However, next time someone tells me it's unnatural for a child to learn that their teacher, family friend, or relative is gay, then I'm going to point right at this video.
In the spirit of sensitivity to others' faiths, I'll say that it is okay to teach your child your religion. However, unless his parents have broken from the commonalities of Southern Pentecostal churches, it is sad that he has a long road ahead of him battling the misogyny, homophobia, and uneducated brainwashing so rife within those communities.