Thank you all for the advice.

He is actually talking to me right now. I sent him a link to "What is Child Abuse" and asked him if he was willing to get help. He won't. He is being very stubborn so it seems I am going to have to go down the path of trying to keep him out of the child's life or have him around only if I am around.

He is talking about how he dislikes today's society. He is now bringing up how there are nudist households (I am fine with nudist households. The thing about those environments are they are always nude and they are not trying to draw attention to their genitalia to teach a child about sex.) and saying how in the 1950's families had baths together. He is saying he hates this society.

Sadly, I asked him to get help about this to maybe talk to someone and he refused. So he does not want help.

He keeps saying "You do think I am a rapist".

I'm saving the chat log I am having with him though I am not sure it will do anything. He even told me to save it since he even said it could get a restraining order on him from the kid.

Now he has went to verbal abuse:

He wrote:
“Up to the age of 4, teach kids the names of their body parts; from 4 to 8, explain how babies are made; from 8 to 12, explain what physical changes to expect; from 12 on, talk about decision making, sexual health and protection, suggests Dr. Justin Richardson, coauthor of "Everything You Never Wanted Your Kids to Know About Sex (But Were Afraid They'd Ask)."” (Springen)

I said:
Talking, not showing.

He said:
I'm looking for where it was recommended.
You "insert the swear word he called me here".

I said:
There is no where that it says "Showing your genitalia."

He said:
It was for the mother and father to appear naked together and explain their bodies.
In a loving and caring and educational context.
Not, EXPOSE GENITALIA.
That is the difference.
And, I am honestly completely offended.

I said:
Honestly there are other ways then to expose an adult body. It is still exposing your genitalia when you are an adult.
There are photographs in books and online.

He said:
How can we expect our daughter to come to us about a problem with her body if she knows we are offended to show our own.

I said:
Many girls have grown up fine without being shown their father's genitalia.

He said:
We are basically saying, "if you have herpes, too bad"
Many girls have grown up HAVING SEEN their father's genitalia and been perfectly fine too.
And their mother's genitalia

I said:
Well by walking in on the father BY ACCIDENT.

He is going on and on. I am going to save this whole conversation.

So right now he is trying to find a site where it says you should show your genitalia to a child.

I am not sure what my next move should be. Is there anyone I can report this to? If so, who?