sure he was...My dictionary defines a heretic as a dissenter from established religious dogma, a baptized member of the Roman Catholic church who disavows a revealed truth, one who dissents from an accepted belief or doctrine, a nonconformist.....pretty much describes old Martin doesn't it???.....what issue was he correct on that the infallible church was wrong on???
I'd get another dictionary, and then study the etymology of the word.
It is first used in Titus 3:10, long before the RCC came into existance, so any definition attaching itself to the RCC is proven wrong.
Here is Webster's definition, which is more accurate:
The word “heretic” is now commonly applied to one who holds some fundamental error of doctrine, “a person who holds and teaches opinions repugnant to the established faith, or that which is made the standard of orthodoxy.” Webster. The Greek word here used αἱρετικὸς hairetikos occurs nowhere else in the New Testament.
The only issue left to decide, is whether or not the RCC is fundamental or otherwise orthodox. That has already been decided. Blessings.