It depends on how the word 'slavery' is defined. The OP defined slavery as imposing upon the rights and freedom of the individual to obey their beliefs. Whereas most dictionaries define slavery as 'The condition in which one person is owned as property by another and is under the owner's control.'
I would use the latter definition as being correct. If a religion (or culture, group, or citizen, etc.) owns people as property, I agree that this is not OK and should be fought against.
Fair enough. I don't think I can name an instance in religion where a person "owns" another. On technicality, I would agree then.