Protecting your community should be job one. They need to feel that you will stand up for them.
In some cases, you can let other fans deal with the commenter. But if the commenter crosses a line, you need to decide whether to delete the comment and/or ban them from your page.
Remember that hurtful comments about other Facebook communities should not be tolerated either. Maintain the highest level of respect for all people as your baseline – it will surely benefit your organization in the long run.
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