well, that's a psychological field of a different nature.
that's dealing with group psychology/group think.
in my opinion from everything I have read on that subject, very generally speaking, it's takes speaking to individuals apart from the group dynamic.
think herd mentality. the herd defends the group. but if you are able to get one of them along, very generally speaking, and have an adult conversation with supporting arguments, most normal people will see both sides.
but as long as the group is criticized in general, the tighter the group will close ranks.
the best example from history is nazi germany. that's a classic example of group think.
remember this rule of thumb, it's never the majority that takes control, it's always the most vocal minority. everyone else follows out of fear.
that's why it's very important to stop that vocal minority in it's tracks at the beginning rather than letting it take control of the conversation.
Sadly, we are beyond that now. 
once it gets to that point, it gets harder and harder to separate out the individuals to convince them to do otherwise.
if you noticed after the first charlotteville demonstration by the alt-right, right after that, social media started identifying the people involved. many came forward and started back peddling and denouncing the alt right. The very people they were marching with.
as time passed that will get more difficult.
again, just my two cents from my armchair. 
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