Where do I draw the line? Well, the stuff listed in the above post certainly doesn't classify as Christianity. There's a good reason why the Church doesn't generally consider the Jehovah's Witness and Mormon (faith, cult, whatever they are) to be Christian.
Most practicing Muslims have a true respect for Isa and Miriam, but we don't consider them Christians either (Yes, I've read St. John of Damascus on this).
Just because Jesus figures in somewhere to someone's faith, it doesn't mean that it's Christianity.
How God classifies people is a very different topic. I'm pretty comfortable with my Archdiocese' understanding that Trinitarian Christians generally count, while others don't. I think a faith/denomination's acceptance, even if not formally, is an indicator as well.
(Joseph Smith was a Mason).
True, but to be fair, he was a really bad one and apparently only completed the first degree.