Odo links with the female changeling and makes her change her mind on a lifetime's worth of hatred and distrust of the solids in about half a minute.
Honestly, I have always viewed that very differently. Odo almost died because of a disease that Section 31 tried to use to commit genocide against his people. Add that to the fact that the Federation was perfectly happy to let him and his people die, and I would think that everything that the Female Changeling tried to tell him about solids finally sunk in. I think when he linked with her, he expressed this feeling and told her he would build up the Dominion and cure his people, and her surrendering would give him the time he needed to do it.
If there would have been a DS9 movie, Odo should have been the main villain. He would have been perfect, his reasoning (though flawed) would have made sense to him (and that's one thing that a good villain always needs, to believe that what he or she is doing is the just and moral thing to do). He would have been conflicted over turning against his friends on DS9, and that would have been the thread that would have been used to ultimately defeat him.