How do you protest a cult?

I want to be hard hitting but fair. I don't want to be boring but personal. I don't want to guide them toward a Christian church as I am not a Christian and want to allow them to provide freedom from religion. I believe I will keep someone from being deceived into avoiding important health measures, protection from pedophiles and rapists and to keep their family united despite religious differences. I know I can't actually reach cultist but maybe it will help the community. Any ideas? I don't want to name names since it will be implied that I am slandering them unfairly. I am ready to back up what I'm saying with evidence and witnesses. I'm not ready to stand outside their church but spread information that the cult won't provide themselves. If they choose to join, at least they will know what they're joining. If they're a member they will know what they're a member of..How would you do this?