Anathematize derives from anathema, which is a Greek word for 'a curse', or the expression of a desire that God may abandon the person cursed. Nowadays, anathematize has lost much of its religious meaning. It usually means "to express disgust or disagreement strongly", often leading to such proposals as one to expel the offender from the association, club, party etc to which both the person offended and the offender belong. Do not use the word
anathemize instead. It may seem better to you, and some people do use it; but although OED does recognise the word, all it says about its meaning is that it "= ANATHEMATIZE". It adds that anathematize is derived from ANATHEM or ANATHEMA + -IZE, "the Gr. stem anathemat- being neglected". In other words, anathemize is an error: it is just anathematized with a syllable left out, through either ignorance or laziness.
If you want to be considered a good student, try to avoid your tutor's anathemas, by being neither ignorant nor lazy. Use the traditional anathematized instead.