Religious beliefs do matter because they affect every part of a person's life. That doesn't mean that everyone should have to conform to the majority belief, however. Everyone believes in something - even atheism is believing that there is no God, when this cannot be proven. I think everyone should have the right to believe what they believe teach that to their children.
For example, the OP mentioned evolution - the vast majority of people in the UK do believe the human race came into existence through evolution, but it isn't a proven fact like other facts in science. It takes just as much faith as believing God created us, to think that there was nothing, then life evolved in single cells, and now we can see, feel, have conscious thought and emotions, etc. How did the eye evolve when it wouldn't have served any purpose until every part was in its proper place? Nobody was there to observe evolution happening and nobody can repeat it in the science lab. I understand why most people believe creationism shouldn't be taught in a science lesson, because it is a minority view and makes no sense if you don't believe in God, but I don't believe evolution should be taught as fact in a science lesson either, just as the main theory. If you don't believe in God then it is the most accessible and acceptable explanation for how things came to exist as they are, but it isn't proven beyond reasonable doubt.
There should definitely be freedom for people to express alternative beliefs and teach them to their children. Just because they're in the minority, doesn't automatically mean they're wrong. The cases that have resulted in needless death are different because nobody has a right to take away a person's life.
Incidentally, the tragic case in Ireland shouldn't have happened because Irish law allowed for abortion to save that mother's life.