Sakellariou's book may be used as reference in many places. Because he is Greek, it does not mean his book cannot be used. But within this article, and for this topic, no. This is a sensitive issue and cannot pretend that he is NPV. It is like me bring in articles from Cham authors stating how the Zervist army did this and that. Also, I remember adding some editing long ago, and Edith Durham, Stavro Skendi, Person, Robert Elsie were considered not "NPV", just because they stated things the Greek editors would not prefer to include. And Elsie and Pearson are used much more than Sakellariou, you can easily check.  

Dr.K, thank you for threatening me. At this point I am getting used. Everytime there is some edit which the Greek editors don't like, I am being left a message in my talk page. As per your suggestion, I already had opened a talk section for discussion as you can see. Meanwhile I would strongly suggest you go on and revise the neutrality of the references provided as NPV by my Greek colleges. Seems that no one is worried about the neutrality of the article, but rather defending what Sakellariou wants to say.
Also, If you check the page's history, you will see that Alexihoua reverted my edits first. So try to talk to him too.