Standing per se was never 'unsafe'. Hillsborough was a disaster created by poor policing and subsequently covered up by corrupt policing. Laws made in knee-jerk reactions are almost invariably bad laws, and the requirement for all seated stadia was one of the classics, and is widely accepted as such.
To suggest that standing areas returning will also lead to casual violence and racist chanting is patently absurd. I never met anyone who became more violent or racist when stood as opposed to adopting the seated position!