This is a very important part of telling people who Jesus really is. Generally, I do not like to call out certain groups, but at this point I have to mention Mormons. When I was young, Mormons identified themselves simply as “Mormons.” They didn’t actually claim to be Christians. Today, they do.
I do not believe God has given us the job of “judges” over individual “souls” or “people.” I tell people that God did not put me on His “membership committee.” It is not up to me (or you) to determine who is saved and who is not saved.
However, I do believe we can judge the doctrinal beliefs of different “religions,” and this includes Mormonism.