So long as an organization is not harming others and is not trying to avert taxes they should be allowed to refer to their organization by any designation they wish. It is not up to the government or other organizations to choose for them whether they are religious or not.
There are all kinds of tax and business filing designations for businesses depending on what they are and what they do. They should be able to choose their own designations, but then they should also have to live with the fallout of that. If they want a peaceful designation they should be monitored to ensure that they meet the qualifications.
I don't think there should be any hard and fast law stating that a peaceful organization that equates itself with a religion should not be able to label itself as such. If the members of the organization feel a connection to religion, I don't think it hurts anything to make that public.
Religious adherents no doubt find that their actions in life are influenced by their religious beliefs. The association between religion and violence is long-standing. To prevent the sectarianism and isolation that leads religious groups to the most atrocious actions is a difficult task in a free society; people are free to join groups and live with friends (call it a commune if you want), and are also free to believe crazy things. To stop social groups, even just exclusive ones, is a severe reduction in freedom and almost definitely not worth it on the balance. Restricting living arrangements would disrupt ethnic groups, religious groups and all kinds of innocent behavior.