A person can call themselves what ever they want to call themselves but can the people you have described truely say that they are Sikhs and try to attempt to live by our Guru's teachings and understand their message. You commented that they feel that sikhi is in themselves and not in the identity. True to a extent but if that was the case why did our Guru's have to initiate amrit from the very beginning and in the end Battea the amrit. Remember our Guru's used to administer amrit but it was called Chaurun Paul but Guru Gobind Singh ji changed the process and started Khande Paul, Battea the amrit. Personally I feel that these people are claiming like quite a few people that sikhi is just inside feelings and not identity aswell. PLease note that Guru Gobind Singh has even stated that "Rehat piyari mujh koa, sikh piyara nehi" He's even stated that "Rehat bina neh sikh kahavea, fir dhar chota kahvea," please excuse me if i've got the quotation wrong but the Guru's have stated that in order to be classified
and identified as a sikh you need to have a identity. Even in life today individuals can be recognised or identified for there personal appearance and their outer attire. SIkh's can be identified due to their turbans and visuable panj kakars. PLease also note that in history it has been noted "that a very holy person from Sat Jug had buried himself in a pot and was found when GUru Arjun dev ji was finishing the Harmandur complex, when awoken he was asked what he was doing and how long he had been in this condition. he replied that he had been sitting there since Sat Jug and have been waiting for a person called Guru Arjun in order to receive amrit from him." Apparently after receiving chaurun phaul he died and left this world. I think that maybe that your freinds need an identity personal one it is the same for Sikhi and Sikhs they need an identity for people to recognise and principles to be guided by. Religious muslims can be identified due to their clothes and appearance, religious hindu's etc.