There’s a very big difference between being a Christian and preaching to the world about it constantly. Out of the 2.4 billion only a fraction insist on letting you know it in everything they do.
Well it depends on whether you consider everyone that claims to be or is assumed to be by default, a Christian, and what exactly you mean by “constantly.”
A true Christian will by definition be preaching the gospel to the lost and dying world at every opportunity
This isn't true (but bizarrely, heartened me, until today I've only seen this sort of overly literal fallacy deployed against Islam)
Usually people use words so that other people will understand them. If your internal definition doesn't match nearly anyone else's, maybe you're using the word wrong.
So.. I’m wrong because the people disagree. An appeal *ad populum* if you will.
Isn't that all language is? An appeal to what others think you mean? This ofc is why people like to push definitions in different directions. I think you're saying, "Christian should mean XYZ," while I'm pointing out most people don't hold your meaning. If you want everyone to adopt your definition, you need to give a compelling reason. However, I've heard so many other people who call themselves Christian claim that all the other so-called Christians are not really Christian, that I don't really trust any particular Christian's definition. It's easier to just say, "Christian means someone who claims to be Christian".