When you are opposing those you considered as adversaries because of selfish/personal issues and not for the sake of Islam/truth; you end up committing grave sins due to your hatred&lack of objectivity.
The one who is committing grave sins now and since years back all started because of his hatred towards his adversaries he considered “Ahlu Sunnah” and he has been doing that without objectivity, just because he wants to fight them anytime and anyhow. He will keep on falling into heresies until he clears his mind off hatred and sees issues with objectivity and separate personal issues from religious affairs.
Same as the Salafiyyah group who wants to refute their adversaries anyhow and anyway and other groups refuting one another too.
What should be dare to each and every caller is the truth and that should be what we should defend with clear evidences from Islamic sources; even if what we realised to be the truth (from our thorough research via reliable Islamic sources) is the stance of our adversaries. And let every caller learn how to separate personal issues from Islamic judgments on matters. You may have personal differences with a person, but that shouldn’t stop you from being objective when criticizing or accepting the person’s views on Islamic related matters. Take control of your emotions and ego when discussing religious affairs; discuss only with intellectualism.
At the end of the day, each of us will be judged by Allah on how we spent our time on earth!