It’s certainly possible that there have been Catholic apologists who have treated Protestants and Protestant beliefs unfairly. But without specific statements of the Catholic apologists from the Protestants who actually heard the alleged remarks, there is nothing that one can say in response to the allegations because there is no way to know if the Protestant listeners were spot-on accurate that there was an actual attack, misunderstood what was being said, overly-sensitive to constructive criticism, or disingenuous. Or, to make matters worse, we don’t know if the person you spoke with is reporting what he said he heard accurately or if he misunderstood or if he is being disingenuous.
Rather than continue such a fruitless argument over who said what to whom and how they said it, bring the conversation back to the original topic: an anti-Catholic remark you believe was made by this person whom you contacted. If your assessment that the remark was anti-Catholic is accurate, one cannot defend himself against the charge of bigotry by claiming that others are also engaged in bigotry. As it is his comment that is under the microscope right now, not anyone else’s, a proper defense would be to explain how his remark should not be understood to be anti-Catholic. Acknowledge that Catholics are imperfect and sin and then politely insist that he answer your initial charge that his remark was anti-Catholic.