I don't mean to be a Dominion apologist, but it takes two to war.
It takes ONE to be determined to conquer and to start a war.
And if the other side is stupidly suicidal enough to not defend itself by firing back, it will lose/die.
Starfleet was always meant to be a force for good (much like America's modern navy, if the ads are to be believed), and the moment they stopped acting like that, they damned themselves to an interminable war.
The moment the Dominion was determined to start the war AND acted to start the war (sending huge fleets through the wormhole/attempting to kill BILLIONS in the bajoran system), war was upon the Federation, regardless of its choices.
Indeed, the Federation's only choices were to fight or surrender to slavery under the Dominion (AND the occasional genocide - as per Weyoun, Earth being first in line to be sterilized).
PS - You make your argument no favors by prasing Odo; his success was possible ONLY because Section31 infected the founders with a virus meant to kill them all.
By sanctioning this meas to end the war, you indirectly sanction actions such as Section 31's.