Re: SHAITAN-------IBLEES
Dear Brother … Intention of the writer is simple, that is, he was giving information or mentioning what is known to most Muslims … so, he was not saying anything new that he has to justify.
It seems, what is bothering you is, how can Iblees, who was Jinn, became leader of Angels. To understand this is simple, that is, it was not his (Iblees) merit, but it was Allah who appointed him Sardar of Angels. I hope you do believe that Allah has right to do that, don’t you? 
Well, not only that, but even when Iblees was thrown out of that position, he was still given power by Allah that he managed to enter Paradise (Jannah) to misguide Adam (AS) and existed from there too, something that no ins or jinn can do.
Well, Allah making one of his creation or individual from that creation above other of his creation, is right of Allah as well as Sunnah of Allah … and there is no reason to get surprised about it.
For example: Allah has given authority to humans over many of his creations that we experience every day of our life and never question (human riding horses or camel, having pets, domesticated animals, and even fish and birds, etc). We should know that Angels, Jinns or humans are creation of Allah same way as horses, camels, goats, cows, sheep, dogs, cats, dolphins, doves, and so on. Only difference is the character what Allah gave to his creations, but then, that is also dependent on what Allah desired to give, else, Allah can make a bird talk and a human dumb.
I would have given you examples that Sulaiman (AS) was given authority over Jinns by Allah and no one feel confused about that, because we know that Allah has authority to do that. Same way, we believe that Prophet (SAW) is considered blessing for all of Allah’s creations living in any world (Rahmatul-lil-Alameen) and no one doubt that … so, why doubt or question that Iblees was made Sardar of Angels by Allah. But, what I want you to understand is that, instead of questioning, ask yourself that what is mentioned or claimed, is it beyond the authority of Allah?
Sure, just for sake of knowledge or understanding, you can ask that, was Ibless Sardar of Angels?
And answer is that, according to many knowledgeable Muslims, Iblees was very pious and ibadat-guzar … and was made Sardar of Angels by Allah. Actually, it is believed that when Allah ordered Angels to prostrate Adam (AS), being Sardar of Angels, this order automatically became applicable on Iblees too … or Iblees being leader of Angels got bounded by this order.