Character consists of more than design, as a person is more than their appearance. The WxY argument takes care of that concisely and has been covered in the past. Chances are even 'normal' people know intricacies of certain fictional characters' personalities from TV or literature better than they know many of their acquaintances. If these traits are things that create an emotional response, feeling love for a fictional composition of personality traits is not necessarily a more harmful thing than feeling love for the image you create of a real person with similarly attractive aspects, out of your reach for any multitude of reasons. Either becomes negative when they cause interference with normal function, but I don't think making sure people have less love is a higher priority than combatting other social or emotional deficiencies.