Zoidar, you say, "But if an unbeliever asks: "Did Jesus die for me?" [Calvinists] can't say anything".
But they most definitely can say something. From my point of view, and, of course, depending on how much they know about God and his Gospel, the first answer is, "do you want him?".
You could, but could not say "yes" or "no". Does it have to be a problem? No! Can it be a problem? Most certainly.