Amazing! First the only hadiths accepted are the "hasan" ones. Muslim, Bukhari, Tirmirdi, Dawood. The other hadiths are not authentic and should not be quoted. Second being you are such an expert on Islamic rituals and laws you would realize that one of the biggest harams is talking about the dead in any sort of bad way.
We are told to dye our grey hair and dying it black is traditional. Should he not have henna then using an alternative dye is permissible.
Also in Islam, Mr. Expert, "If you do not have anything good to say, you are to remain quiet.