Shatpath Bramhana says that brahmin boys should cover their bodies with skin of Black Deer or Krishna Mriga (Black Buck), and this is okay if they don't just kill them for that purpose. A dead buck's skin could serve the purpose, then why hunt for it?
There are some stages in Shodashopchar (16 stage treatment or pujan of Gods/Goddesses) where Ashtagandha is required which uses Kasturi or Deer Musk as one of the product, and some Goddesses also require Deer Musk and sandalwood paste for their worship.
So the point is that Deer Musk and Black Buck's skin are obtained from killing the specified animals.
My question is:
1) How is it justified to kill someone so that you can worship some Gods?
2) If Manu Smriti says that Dwijas are required to live in the area where Krishna Mriga or Black Buck lives then why to kill them and make them extinct.