The tone in the link I provided sounded as if Catholics, or at least the ones that wrote the article, look at Jehovah's Witnesses as some sort of offshoot or schism.
I agree that it is a schismatic religion, but not from the Catholic Church per se. In the narrow sense, Witnesses are many branches removed from Catholicism. I understand the lineage is (please forgive any omissions on my part): Catholics --> several Protestant groups --> Second Adventists (Miller) --> Bible Students (Russell) --> Jehovah's Witnesses (Rutherford, Fred Franz). (Yes, Rutherford's coup d' etat was a schism--Russell would hardly recognize what the Watchtower preaches today.)
In a wider sense, Jehovah's Witnesses are a schism from Christianity as a whole: Catholic, Orthodox, mainline Protestant, Baptist, Evangelical, Pentecostal, all other believers but themselves--and they're mighty proud of it! If the Watchtower takes offense at being called "schismatic", that's because the word implies legitimacy of those from whom they have separated themeselves--the ones they call "Babylon the Great", "False Religions", "Christendom", etc.
So Schism--yes, but Catholic--not in particular.