Then again, the "good" qualities of the Federation also mean the UFP will be a safe haven for forces bent on destroying the Founders. It fosters belief in the value of personal and communal freedom, which is the antithesis of the one and only Founder means of keeping anti-Founder sentiments at bay. It also currently stands as an inspiration for anybody who wants to oppose the Dominion by force of arms. For this double message of "resistance is not futile", the UFP simply must be defeated and enslaved, now more than ever.
Thanks to Odo, the Founders might feel sorry for having to do this, but that doesn't change the necessity of the act.