Point out that the Inquisition was intended not to convert people, but to find people who were outwardly claiming to be Christian but secretly practiced another religion, such as people who had become Christian outwardly, but who were still secretly practicing anti-Messianic Judaism, Islam, or Albigensianism, this last being a religion claiming that there are two gods, one good and one evil. The inquisition was thus an attempt to protect the purity of the Christian community.
Also point out that the Protestants had a counter-inquisition that killed Catholics. Thousands of Catholics were killed in England alone after the Reformation struck there. The same thing was true in Ireland and other areas where the Reformation came. John Calvin, for instance, was known for burning people at the stake.
In addition, Protestants were the big witch-burners. Witch burning never caught on in Catholic countries. When the Spanish Inquisition examined the cases of reported witches, it almost invariably concluded that the charges were false and the accused were not guilty. But tens of thousands of supposed witches were burned at the stake, hanged, or drowned in Protestant countries, including the American colonies.