25 Year-Old Japanese Man Arrested For Allegedly Threatening To Blow Up Nintendo's HQ

That's not what you said in your previous definition. You had already proven that it isn't mere slang.

Yet fanboy's slang context is by far the most common one used. Slang does just that, takes words and corrupts their meaning to be used in a different context, giving it new definition(s)... or creates unofficial words altogether.

So yes, someone that could be accurately described with the slang, derogatory connotation of "fanboy" (#4) is lamesauce.