The nominal Christian is a problem for Evangelical Christians because they like to count them in the census results when looking for evidence that Christianity is still the main religion of Britain, or count them as Christians when looking for evidence of persecution in countries like Egypt and Iraq. Yet, if these same people were to turn up at their church on Sunday they would not be considered Christians at all.
This is an example of the sort of intellectual dishonesty common among fundamentalist Christians. For example, saying they believe th bible is literally true while allegorising the heck out of the books of Daniel and Revelation.