A few things I'll say about this episode are - 1.) Keiko is an idiot and 2.) Sisko made the wrong decision.
I've never understood the hatred for Keiko that some fans feel. Overall, I think she's a good character. But in this episode, she's really out-there. Like Shatnertage
said in his review thread - here she is, making dinner for two guys with clear and known problems with Cardassians and she makes them Cardassian food. Good grief lady! And it's pretty odd that right after she (rightly) calls Miles on his latent racism against Cardassians, she shows some herself. She thinks Rugal will like Cardassian food simply because he is Cardassian. That's almost as bad as her saying "Here you go, I thought you'd enjoy some fried chicken and watermelon since you're black."
If she wanted to make him feel at home, how about some Bajoran food for crying out loud.
As for Sisko - his decision to send Rugal back to Cardassia was wrong. What he should have done was have Rugal remain with his Bajoran parents and have his biological father slowly get to know him and become part of his life. That way all the parties are happy. Simply ripping him away from everything he's ever known, forcing him to live with someone he resents and essentially saying "here you go, deal with this, bye" isn't going to make him love that man.