The evidence would seem to indicate that the Cardassians had aggressive behaviour prior to the signing if the treaty.
One outcome of not signing the treaty could have been another war, so which is more important the safety and wellbeing of the hundreds of billions (if not close to a Trillion) of others or at best maybe a few tens of millions of border worlds which you have offered to resettle elsewhere?
Perhaps it was not so much the treaty that was at fault, but either Starfleet Command or the Federation Council or both for failure to act over possible Cardassian Infringements. Increased patrols, escorting of transports etc.. Flying he flag in a more visible way.