Taking a life is a huge deal, even the animals we slaughter we ask for Allah's permission before we take it and the Quran has clearly identified and stated when taking of a life is allowed. So how can we make up rules that call for the paying the ultimate price based on words of men i,e hadith.
And when Allah s.w.t does not prescribe this for the biggest and most unforgivable sin, i.e associating partners with him or saying he begets or is begotten, you think he would prescribe this for a lesser sin?