I'm not defending Mormonism, however I not offended that Mormons find me, a Roman Catholic, apostate. I find them apostate too. And Lutherans, and Calvinists, and Baptists, and Eastern Orthodox. So what?
Obviously, Mormons are further from my Catholic faith than others since Mormons don't believe in a Triune God. But it's hardly surprising or troubling to me that Mormons would find me apostate. In fact, their faith is so far from my own that I would hope they would.
Excellent fresh observation offered on here...thanks for injecting it!