Although I would contest the "only", as there are other contexts
  where they general or abstract terms can exist, depending on
  what one considers valid evidence.

  "Does Love Exist?" - looks up concept, finds analogy that ties
  concept to something tangible. The something tangible might be
  behavioral, societal, a statue of Love, Laws of Love, etc... all
  of which can lead someone right back to Platonism if they're not
  careful, because it can be said, "Love exists" in _some_ rough
  shapes that seem to correspond to the perfected forms, therefore
  the perfected forms must exist somewhere... and... of course,
  they do...

  ..as written in the place you read about the concept.