Restricting "Christian"

I'll try to keep this short, but I think I may be onto something here:I would like to propose a new restriction on using the word "Christian".

People should no longer be allowed to self-apply the the term "Christian". Instead, it should be up to everyone you interact with to determine whether you are a Christian or not. Your spouse, your kids, your boss, your employees, your plumber, the guy at Subway, homeless people, cops, black people, homosexuals, everyone.

What would they say you are?