Christians yes but also heretics.
Well, we all know how that turned out, don't we, with about 650,000,000 Protestants in the world today.
And they are not even the largest group of heretics around today: Catholics, with their "filioque", are, unquestionably, heretics from the Eastern Orthodox standpoint.
Hereticism is not a slur - it is a designation. From a certain standpoint, nearly everyone is a heretic.
Still, Mormons are further away then the rest. Catholics would recognize nearly every baptism as Christian. As you aren't supposed to be rebaptized if you were baptized once already, this means that pretty much any protestant would be, from the Catholic standpoint, considered Christian (albeit, indeed, probably a heretic) from the moment of his baptism. However, a Mormon baptism is simply not viewed as a Christian sacrament, heretical or not, by the Catholic church. There is quite a bit of a difference there.