Sisko didn't commit murder. He gassed the planet, but IIRC there's no mention that the gas would be lethal, and the Maquis were able to leave the planet in any case.
Honestly, sometimes it seems like people deliberately distort the events of the episode just to serve their argument.
It was the best of Trek, it was the worst of Trek...
"If I lean over, I leave myself open to wedgies, wet willies, or even the dreaded Rear Admiral!"