All of this depends on how you term what a Christian is and what kind of criteria you use to make that desicion.
Here is my own criteria based on the solid theology of the Catholic church:
1) Christianity is a fact not a feeling. this means to be a Christian is a real thing not just a concept or a mere internal(heart) thing but a actual real solid thing as well(As by external covenant oaths and real grace recieved from them ie..Sacraments).
2) while I should never and cannot ever judge if anyone is going to heaven or hell or anyones heart(Jesus told us not to judge hearts), on a outward principle I can judge criteria that would make someone a "Formal Christian" or joined to Christ formally by covenant bond and sacred reality.
3) Some would say that a Christian is a person who loves, accepts and follows Jesus Christ and believes in his death and resurrection for us. While all of these elements are essential for christianity, I believe they are only a partial list. Anyone can say I'm a Christian I believe in Jesus Christ, Hersesies have done it for centuries just study the early church. The real question is do you believe in the Jesus of Nazareth that the historic Christian church affirms or do you believe in another Christ. This is something that St Paul wanred about in the book of Galatians.
For example,. Am I a "Christian" if I believe in Jesus Christ and his saving work but I believe that Jesus Christ is a magical donut?? Absolutley not! I must believe in the real Christ, the true Christ and true Gospel. In a likewise manner Many will call themselves Christians but will believe that Christ was merely Michael the archangel or a perfect man and not God almighty. Some believe that Christ was merely "A" God among many? Trinitarian Baptism is the formal gateway, covenant or entrance to formally becoming a christian as understood by the historic Christian church from ages past. So understanding and believing Christ Jesus true nature and formally covenanting with him is essential to understanding and believing the "real" Christ of history and being a true christian in the "formal sense".
4) This does not mean that the non-Christian or even pseudo-christian has no relationship with God. They very well do have one. It only means that in the true formal sense of the church, they are not Christians. In their hearts they may wish to please Christ and love Christ and Christ will judge them according to that. And through this, Christ may mystically unite them albeit impartially to the Church for salvation, but in the truest "formal" sense of the reality, they are not Formally Christian and we do not consider them to be.
That is my theological Catholic take on this issue. Feel free to dissagree!