McKim points out that people hold a wide range of different views about religion, they hold their opinions strongly, and they are convinced that other people who hold different views are wrong. He thinks this important, because it shows that people should be more tentative about their beliefs.  One assumption made by McKim is that people who hold different religious views really do disagree with each other. This is controversial, because some have argued that while it appears that different religions disagree, they all worship the same god, and other disagreements are superficial. But as McKim says, the different religions certainly seem to hold significantly different views, about the nature of God, for instance. McKim thinks that whatever God is like, if there is one, is mysterious. Religious experience does not make the nature of God very clear, and does not support any one view unambiguously. But it is the very fact that serious thinkers, who seem equally qualified to talk about the issues, manage to disagree deeply that McKim takes to be the main reason for thinking that religion is mysterious. He does note that there are some things about which many people disagree because they do not know much about them, and if they were experts they would not disagree, because the experts have found the truth, although it is complicated and hard for non-experts to understand. McKim makes another qualification to his argument, saying that if disagreement can be explained away if someone holds her view because of some defect in their reasoning processes. But if the views of two or more of the parties disagreeing cannot be so explained away, then there is reason for all parties to the debate to be tentative about their views. Being tentative about one's views is different from suspending one's beliefs or abandoning them altogether. One can still hold them and one cannot believe one is right. 

What is McKim inplying here?  Is he saying there is no point to disagree since we are all worshiping the same God?  Can anyone help me make since of this?