What should we do when we see devotees fighting with one another?
In Caitanya-bhagavata Srila Vrndavana dasa Thakura says that when you see two Vaisnavas fighting you should know that it is the Lord’s pastime. Therefore it is offensive to take sides. But Vrndavana dasa Thakura is talking about elevated Vaisnavas, not aparadhis. If you see two advanced Vaisnavas seemingly opposed to one another, consider it lila; don’t become an aparadhi by taking one side over another. And if both are aparadhis and are offending one another by their behavior, then it is still best not to get involved. However, we have to be careful not to judge that something is an offense when it is actually not. Prabhupäda said that we must speak the truth, calling a spade a spade. The truth is sometimes unpalatable, but we should not refrain from speaking it. But if you see that a person is actually being offensive in their behavior, then “taking sides” may mean that at least you try to get the dispute resolved by someone who can help. Simply taking sides and even starting a defensive movement is not the way to resolve problems. We do not solve problems by numbers or by creating a vox populi. Rather, we should resolve problems from the spiritual platform. Therefore we should look for people who have the most Krishna conscious influence on all parties and place the dispute in their hands.
(LFD, Vol2, Becoming Free from Sin, Pg 43, last paragraph)