I love your point and honestly, it's something terrible for a child to change from his or her parents religion. For me, it depends on the religion because I believe that there is only one God and as long as you worship that true God, we might not have problems.
On the on other hand, training a child as we should wouldn't make them change to what's not expected of them.
True, I see religion as a point of contact between your child and his creator, messing it up can be disastrous. This is why the child should be tamed on the right religion to avoid backlash.