I don't think is is true at all. In anything, the past was much more into reporting sensationalist news about murder than now. The infamous UK "News of the World" tabloid, which existed to give titillating reports of murder and rapes, started publishing in 1843. It closed in 2011 in the wake of the phone hacking scandal because society began to care about victim's rights. The idea that the past was more moral than the present is just rose-tinted nostalgia without support.