I don't think I could connect Jones or Yiannopolous specifically to anything, just as I couldn't connect, say, Andrew Wakefield to any single specific case of parents forgoing vaxines.
I also think the ideas that Jones and Yiannopolous promote are easily seen to be harmful. Yiannopolous has promoted violence against journalists and associated himself with white supremacist movements. Jones has promoted the harassment of many victims of crimes and generally undermined public trust of institutions (including limited support of anti-vax views). I suppose it's up to you if you feel those ideas could cause harm - I feel they (and other ideas both have promoted) do.
I also think the ideas that Jones and Yiannopolous promote are easily seen to be harmful. Yiannopolous has promoted violence against journalists and associated himself with white supremacist movements. Jones has promoted the harassment of many victims of crimes and generally undermined public trust of institutions (including limited support of anti-vax views). I suppose it's up to you if you feel those ideas could cause harm - I feel they (and other ideas both have promoted) do.