This story is both heart-breaking and revolting. There is an additional element beside the culture of death, which is that the UK signed the Convention on the Rights of the Child (CRC) which is a United Nations human rights treaty that gives states legal authority to make decisions about a child's welfare whereby the state's authority prevails over the parents' authority. In effect the parents are legally powerless. Note that the US did not sign.
Here are a couple of links if you want to know more:

http://www.ohchr.org/EN/ProfessionalInterest/Pages/CRC.aspx

http://www1.cbn.com/cbnnews/world/2018/april/heres-the-legal-reason-why-the-uk-can-force-alfie-evans-to-die

http://regentfamilyrestoration.blogspot.fr/2018/04/who-knows-alfies-best-interests.html