I know exactly what groups and who you are talking about. I am an atheist, secular homeschooler and I had to leave those groups there was so much intolerance.
Just because someone has a faith does not automatically make them an inferior authority on a topic or a bad homeschooler. I would never use YE science or an overtly religious history program (Notgrass), but I can get over/edit a little religion in a math program (like Horizons), strongly edit and use an overtly religious math program (CLE), understand and explain to my child the religious references to the beauty of God's creation in a non evangelical program like Climbing to Good English, expand a neutral science program (LOVE Nancy Larson) to add in materials and references to evolution, or use a creative writing program that has some separate religious materials (WriteShop Junior). Religion is not the point of any of those materials and I tolerate other people's points of view. I know that as the teacher, my view has the most sway on my child. He lives in my house.
I got so irritated with how overboard/intolerant those groups are to the mere mention of religion, I went in and deleted them all one day. God is not an offensive concept. As long as no one is pushing religion on me and I fine. Live and let live.
Many, many excellent material are written by people of faith. Those intolerant homeschoolers are missing out.