What makes you say Starr is biased? I did a quick look at his background and I'm not seeing anything suggesting a particular bias.
Also, what do you mean, "Nothing to say who they are"? He names every single person he quotes in the article.
Here's a list of just some of them so named, and this is from only the first few paragraphs.
Official Russian war correspondent, Evgeni Lisitsyn
Yuri Devich, Duma member
Andrei Kartapolov, chairman of the Duma Committee on Defense
Commentator Sergei Mardan
Loyal ally of Vladimir Putin, Oleg Matveevich
Moscow tele-journalists, Olga Skabeeva
All in all, he quotes from a dozen or more prominent people located inside Russia.
As for for why they hold the opinions they do, I would say their words are self-explanatory.