A rat's arse is usually something you don't give. So, if someone says "I don't give a rat's arse!" it's just another way of saying "I couldn't care less!" or "I don't give a fuck!"
However, it is possible to give a rat's arse, too. Many years ago a meteorological (Met) colleague working at an Antarctic base opened a crate of equipment that had been shipped to the base many months previous. Inside was the severed body of a dead rat. The rear end was put on display somewhere together with the sign: "Who gives a rat's arse? Met do!"
"I think I've left my homework on the train. Oh well, I couldn't give a rat's arse. It was bullshit anyway."
church hurt is where you experience a degree of distance, pain, or judgement from your church community. Essentially, you are just unable to “find your place”. This is prevalent in the Christian community, but can be extended to other religions.
Now that I am an adult I am beginning to heal from the church hurt that was inflicted on me as a child.