Therefore, a Christian by this world's count, will have to include everyone who wants to so self-identify, and whose conduct is not so outrageous as to result in such identification being widely disbelieved.
Christians also believe in a judgement to come, at which it will be determined by higher authority, who was genuine or real in his claim to be such, and who was just putting on.
Where does the Bible say that one has to be baptized "as an adult?" What is the age one is considered an adult or accountable? Does the 5 yr. old who seems to have a grasp of salvation and baptism have to wait until a certain age for it to really count?