Is it a humanistic value to kill those that leave the religion? https://www.theguardian.com/global/2015/may/17/losing-their-religion-british-ex-muslims-non-believers-hidden-crisis-faith https://time.com/4534504/bangladesh-atheist-blogger-murder-arrest-nazimuddin-samad/
In my view the answer is no, and I assume that the Russian Orthodox Church has the same opinion.
If that is the case then the Orthodox Christianity and Islam are NOT based on identical humanistic values. QED.
Furthermore, the Quran has borrowed a lot of text from the Bible see http://www.freerepublic.com/focus/f-news/1277705/posts and the Bible has borrowed from the Hammurabi Code https://avalon.law.yale.edu/ancient/hamframe.asp
Ths means that there are a lot of common ideas in the texts.
Yep, Quran plagiarized Bible a lot.
As for “pecularities” of Islam see my post #59.
Orthodox clergy are among the biggest critics of Islam. It seems like Catholic Pope is in disagreement with them and so are many Protestants.
Killing apostates is certainly not a founding principle of any Abrahamic religion Islam included.