Well Sisko's anger towards Picard is very understandable. Picard's face was the one on the viewscreen the day he and Jake lost everything. That face was mercilessly telling them it was all futile and any concept of sacrifice was meaningless. And he pretty much was right, that fleet at Wolf 359 didn't accomplish a thing other than slowing the Cube down long enough for the Enterprise to save the day.
Years later that same face is ordering him, a single dad, to take his son to be rasied in a Cardassian shithole in the ass end of space, living with a bunch of religious yokel natives. When he presumes to point this fact out, that same face that took away his wife then presumed to lecture him about duty, when he had already given his dearest blood for it at Wolf 359.
It's not fair at all, but it's very human. That's really what Emissary was about. Sisko moving on from that day. Even the Prophets saw that from the beginning.