I just started watching DS9 and I was a little bit agitated by the way he treated Picard at first because everyone knows what happens to your freedom of thought and action when you are assimilated by the Borg. The real Picard did not wish for anyone to die. Those people died because of the Borg, not because of Picard.
However, I immediately understood why Sisko was so angry...because he lost his wife and had to raise his son as a single parent. That's rough. Even though I am sure he knew in the back of his mind that it was not actually Picard's fault...just looking at Picard's face must have been rough for him and I understood his anger. And it was the first episode...cut him a break. I've only seen the first couple of episodes so far and even though I thought he seemed out of line when speaking to Picard, I do not dislike Sisko at all. He seems to care a great deal about his son and his work.
I understand his anger. And as I've heard, he does realize later on that it really was not Picard's fault. Even in the first episode, they seem to make amends at the end and shake hands.