And there's the problem. You're making a faulty grammatical argument about a pronoun.
If I get on the PA system and say, "Whoever owns the silver Honda in the parking lot, your lights are on," I'm not implying that anyone within earshot may claim ownership of the Honda. Nor am I making any statement about how he became the owner of the Honda. It simply means that of all the people on the premises, one owns the silver Honda with its lights on, and I'm speaking to him.
Similarly, John 3:16 does not affirm that anyone without restriction has the ability to believe in Christ or has the moral capability to believe. It says, simply, that some will believe, and to them, Christ will grant eternal life.