“Religion is evil”
No. People are evil. Evil people use religion as an excuse to behave badly 
“Stop blaming religion they are responsible for their own actions.”
This ^^ with brass knobs on
“They won’t have Christmas tree (too pagan). No Santa or Easter eggs (ditto) No pop music, won't buy newspapers with horoscopes.
My 5 year old grandnephew has had a class in school explaining how Santa and Satan are the same person, including showing the anagram.”
This isn’t Christianity. It is a weird religious cult. I am C of E and we have a Christmas tree in church, the church gets used for all sorts of social events which include drinking and gambling (wine at harvest supper, raffle tickets being sold), the children get given Easter eggs at Easter and Santa makes an appearance at the Christmas fair. This type of thing has always been my experience of Christianity (C of E)
“Yes. She teaches creationism in science class.”
Isn’t that illegal? Or it should be.
“I tend to pity people who are sucked in or need it as a crutch or are lacking the intelligence to comprehend science”
Interestingly most of the congregation at our church are well educated professionals – doctors, architects, lawyers, social workers etc. Probably, like me, they just enjoy the spiritual side and the support of the members of the congregation if they feel they need it. They don’t hold ridiculous views like your sister, they are open minded and are quite happy to accept people as they are. I haven’t been to church for over a year, but I still feel included. I deliver the parish magazine, bake for fundraising events etc. No-one has hassled me about non-attendance. No-one is evangelistic. They are just nice people.
What an excellent post canttestright
“Satan sits on her shoulder waiting for a chink in her defences.” “My sister has a long history of such behaviour, she has tried to get her husband exorcised, would force her own kids to wear black on Easter weekend and have them mourn.”
It sounds like your sister needs help. This is really not a normal way of thinking. Does she suffer from depression or anxiety, or other delusional thoughts? It sounds like she needs to see her GP. How can you honestly accept this as normal behaviour?
Your sister isn’t religious. She is odd and has some strange and disturbing ideas. Should she even be a teacher with her unhealthy views?
“People control, using religion as an excuse. The whole essence of Christianity is free will.”
Absolutely, but many atheists refuse to believe this.
Massive drip feed there. Which country is this school in?