My DP and I are both athiest/agnostic but he comes from a strong religious background. My belief is that children should be free to choose their own beliefs and not have anything forced on them. This includes my beliefs. If he asks, I will tell him what I believe, and what some other people believe, but this doesn't make it true - it's a belief.
Unfortunately, because DP is from a strong religious history my DS receives religious gifts/poems/cards at every event and there are certain family members strongly forcing their beliefs on him.
He's not related to them. It's extremely disrespectful toward my belief that children are free to choose their own path in life, free from indoctrination and manipulation. Thankfully DP and I don't have children together, but if his family members wanted him Christened/Baptised/attend church/whatever I'm sorry but nothing should trump my beliefs simply because they are religious and I'm not.