What this means is that the theist filling out a profile should stop and discard what they've started. Atheist Nexus is a site exclusively for non-theists. What that means is that theists should not join.
As is written on the homepage of Atheist Nexus: " The World's Largest Social Networking Site Exclusively For Nontheists!"
There are plenty of other sites to engage non-theists. Atheist Nexus is not one of them.
The bible has plenty of fine print, but I'm pretty sure that the one unforgivable sin is to deny the holy spirit, and there is no way out of that. That's true even if you have your fingers crossed behind your back.
This site is for nontheists, it's stated explicitly, and if a theist just doesn't get it, that's their problem. Everyone who joins Nexus has to have done so with the knowledge that this site is by and for nontheists.
As an atheist, I need this site. I'm damned all day long. I have to travel five miles to the gym. I counted over 20 churches. I'm a member of RDF. I was reading a post yesterday. Someone butted in "God still loves you". Man, I don't need that. I'm just a regular Joe the atheist. Theist, leave me the fuck alone. I don't want to see you, I don't want to talk to you. I don't want to be blessed when I sneeze. I don't want to see your fucking cross tattoo. I hate that fucking cross around your neck. I'd love to take it off and shove it up your fucking ass.