The Church persecuted heretics not because it rejected the essence of the Gospel—which proclaimed love for one's neighbor—but because, for it, the unity of faith was the cornerstone of the salvation of society and its believers.

Unity and Purity: The Church's Rationale for Heretic Persecution

The Church persecuted heretics not because it rejected the essence of the Gospel—which proclaimed love for one's neighbor—but because, for it, the unity of faith was the cornerstone of the salvation of society and its believers. From the standpoint of official doctrine, allowing heresies threatened to destroy the spiritual community, which was seen as a threat to both spiritual purity and public order. In other words, true love was expressed not only in the virtue of how one treated one’s neighbor but also in the care for the unity of the Church, which was to remain unyielding and free from “destructive” elements. Thus, according to Church representatives, the strict persecution of heretics was a justified means of preserving this unified faith, even if such measures contradicted the general spiritual call to love.

This position is supported by the following reasoning:
"The Church systematically engaged in the persecution of heretics to assert the unity of faith and eliminate the threat of internal division. This was carried out through various legal measures and severe punishments for those who violated the principles of the faith. Sanctions reached extreme levels, including execution by burning if a person was found guilty of blasphemy or heresy, as was the case in the Synodal Statute of 1649 and the naval ordinances of the eighteenth century." (source: link txt)

Thus, despite the commandment to love one’s neighbor, in the official understanding of the Church, preserving spiritual purity and unity was considered the highest manifestation of love for God and neighbor—even if it required harsh measures against those who preached deviations from canonical norms.

Supporting citation(s):
"The Church systematically engaged in the persecution of heretics to assert the unity of faith and eliminate the threat of internal division..." (source: link txt)