WHAT PART OF “CONTENT-NEUTRAL” IS UNCLEAR?

Once again on the subject of strange things arising in Arizona, a town’s sign ordinance that treats signs differently based on what the signs are about has been found to be unconstitutional by the U. S. Supreme Court.  
Of course, it’s not at all strange that such an ordinance would be found to be unconstitutional.  No, the strange thing is that three of the justices seem to think that although in this particular case it wasn’t ok, there are some circumstances in which it would be ok for government to treat signs differently (that is, according to the time and place) based on the content of the signs.