Matthew 5:43 and the Negative Inference Fallacy

You have heard that it was said, 'You shall love your neighbor and hate your enemy.' (Matthew 5:43)

The most interesting thing about Jesus quoting Scripture here is that only the first half of the phrase is recorded in Leviticus 19:18. The verse commands us to love our neighbor, but it's curiously silent on what to do with our enemies. What do we do with them? Or to frame this another way, we're after the same answer as the lawyer in Luke 10:29, when he asked "Who is my neighbor?" since it's really asking "are there people who are not neighbors who can get the category hate?"

This is in fact what the Jewish teachers had done. Using logic they reasoned that if we are to love our neighbor then there is a category of not neighbor that should get not love.
But God hadn't actually said anything about not neighbors and so the teachers were committing the negative inference fallacy to supply the missing piece. The reason God didn't say anything about not neighbor was because the positive category of neighbor was intended to cover everyone, which is why He answered the lawyers question with the parable of the Good Samaritan.

Today some people think that because Jesus says He lays down His life for His sheep that there's a category of not sheep who Jesus did not lay down His life for. Or because He says He loves His elect that there's the category of not-elect who get nothing but not-love. This is not only bad reasoning, it's reasoning openly condemned by Jesus in the sermon on the mount.