I'm with PioneerProgress on the anti-Mormon sentiment being unjustified and kind of bizarre.
Believe in the Holy Trinity - you're Christian. Reject it, and you're not.
Mormons may believe they are Christian, but insofar as they reject the Trinity they are just one of many splinter groups that have done the same thing over the ages.
It seems to me that any definition of "Christian" that excludes the Arians is by definition too narrow. Citing the Nicene Creed as a test of Christianity also seems strange; it's not as though the Nicene Creed was created with Christianity.
