St. Jerome is one of my favorite saints! He never mixed words when it came to dealing with heretics. Here are a few of his quotes. (I will add more later today when I have more time)
"I am told that some one has been mad enough to put deacons before presbyters, that is, before bishops. For when the Apostles clearly states that presbyters are the same as bishops, must not a mere server of tables and of widows be insane to set himself up arrogantly over men through whose prayers the body and blood of Christ are produced?"
"Let my [detractors] take my answer as follows: I am not so dull-witted nor so coarsely ignorant (qualities which they take for holiness, calling themselves the disciples of fishermen as if men were made holy by knowing nothing) -I am not, I repeat, so ignorant as to suppose that any one of the Lord's words is either in need of correction or is not divinely inspired."
"This is what Marcion asks, and the whole pack of heretics who mutilate the Old Testament, and have mostly spun an argument something like this: Either God knew that man, placed in Paradise, would transgress His command, or He did not know."
"Heretics bring sentence upon themselves since they by their own choice withdraw from the Church, a withdrawal which, since they are aware of it, constitutes damnation."
"He slays a heretic who allows him to be a heretic. But when we rebuke him we give him life; you may die to your heresy, and live to the Catholic faith."
"You are renowned throughout the whole world; Catholics revere and look up to you as the restorer of the ancient faith, and -- which is a token of yet more illustrious glory -- all heretics abhor you."