Netziv Meishiv Davar 1:44
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hate was not limited to those who “wronged” a person. Rather, it extended to those who served Hashem differently. If one would see a halachic leniency, he would brand it heresy, and distance himself from that person. He would then mistakenly justify attacking that person, even to the point of murder. The Netziv laments that such internal hatred within the observant community existed in his time (the late nineteenth century) as well. Hating someone who “wronged” us is necessarily limited. With how many people can we fight over money or honor? But if we hate those who differ with us on matters of halacha or hashkafa, the sinas chinam is unlimited.
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[A] review of Neziv�s writing reveals his advocacy of contemporary religious coercion, his description of the non-Orthodox Jew as theologically worse than an idolator, his instructions to separate from Sabbath violators in the religious and social spheres, and a justification for slandering those Jews who �deny the Torah of Moses.�
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related sources:
Sifrei Naso 42: Great is peace, for even if Israel worships idols, if they live in peace, the Holy One, as it were, says that the Accuser (�Satan�) cannot touch them, as it is stated (Hosea 4:17) �Ephraim has bound himself to idols�leave him alone.�
Kalla Rabbati (Chapter 5): �As long as they are joined together, even to worship their idols, leave them alone.�