Why are Christians so obsessed/provocative about non-believers?

The very term `atheists` (add upper-case `A`) was coined by deists as though those who don`t believe gather in non-belief, which is not true. What do they perceive, an opposing army?For no such gatherings exist. is it the relative autonomy with its` attendant differences ans responsibility, which fascinatesor even annoys or scares believers?Or the anonymity? What is it? And answers from Christians will be very enlightening.