The only reason the Bajoran adoption took place was because Dukat did something WILDLY illegal.
Which doesn't change the fact that Rugal was a Bajoran citizen who had been legally adopted by Bajoran citizens. The Cardassian Union and the Federation had no right to abduct a Bajoran citizen from Bajor and send him off to Cardassia against his legal parents' will.
Kotan was setting right what Dukat did.
No, he was kidnapping Rugal from the only family he knew or wanted and sending him off to a world where his son would be raised in tyranny. He had no right to do that; it was fundamentally damaging to Rugal and his developmental health.
And when did Dukat or any other Cardassian official terminate Kotan's parental rights or determine that he could not be a fit parent? That did not happen. For a parent's claim to be totally annulled in that manner is something that the Bajorans and Starfleet had no right to do without a proper and very thorough investigation, which we have no proof, based on the episode, was actually undertaken (on behalf of either side, sadly).
Some sort of joint custody or visitation rights might have been a scenario I could accept. Hell, it might have even been possible to convince Kotan to move permanently to Bajor for this purpose; I know if I were in Kotan's shoes, I would choose exile for the sake of my child if that were the choice presented to me. I would give up EVERYTHING for my child...my home, my position, my status, everything. These would've been the optimum outcome, perhaps, and I think the episode failed for not examining those options (in addition to other things it failed to examine properly). But for you to suggest his parental rights should be completely brushed off--that is really disturbing.
Let me remind you again of this real-life case. Are you suggesting the father has lost his claim because of the illegal thing that his wife did? Those who use the emotional damage done to the boy by his illegal and immoral separation from his father as justification to CONTINUE the separation are way out of line.
http://www.cnn.com/2009/US/06/03/new.jersey.brazil.custody/index.html
Read up.
That's a poor parallel for a number of reasons, not the least of which is that the person raising him did had something to do with the child's initial abduction, and because the U.S. and Brazil have normal diplomatic relations and can resolve this diplomatically. On top of that, that child remember his biological father; Rugal did not.
The idea that Rugal had no memory of his biological father that could ever be retrieved is a conjecture that Una McCormack made. Certainly in the episode Rugal showed no signs of remembering, but in the end we're left to conjecture two different possibilities as to what could happen. One is the scenario that Una went with, which is that he had no memories save the memory of the abduction. The other is that there WERE memories that could have been awakened over time.
I also find myself very suspicious of Proka Migdal here--I do not put it past him to have deliberately induced Rugal to forget, or to have convinced him that any memories he DOES have did not happen. This certainly fits with the self-loathing attitude Proka has fostered in him. Unlike Una, I am not convinced of the purity of Proka's motives; we never had conclusive proof either way on the charges against him, simply a handwave by Sisko after a very minimal investigation. And if Proka has done this, then he is guilty of brainwashing--which is quite ironic considering that the Cardassians are often accused of such things, and almost certainly have done them.
One more point. If you read the case I mentioned again, you will note that the Brazilian authorities are NOT complying with their treaty obligations as regards international kidnapping and have stonewalled the father and US authorities. This obstructionism makes the parallel quite appropriate indeed.
Cardassia and Bajor did not have normal diplomatic relations. Rugal was the victim of intra-Cardassian kidnapping, and his Bajoran parents had had nothing to do with that, thus rendering his adoption legal under Bajoran law. Cardassia and the Federation had no right to interfere with Bajoran sovereignty by trying to de facto render that adoption void by sending Rugal back, as the Federation judge at the end of The Never-Ending Sacrifice determined.
And Kotan still has a legitimate challenge to the adoption. It may have been legal
before the existence of a biological father was known, but after that, there is no excuse for said adoption trumping Kotan's parental rights, unless Kotan is an unfit parent. As far as I'm concerned, we had potential evidence in the episode (which was given a handwave) that Proka was unfit on grounds of verbal abuse towards the child, fostering self-hatred in Rugal as his revenge against the Cardassians. (This claim was never properly answered, even though the physical abuse charges were likely vacated based on medical examination.) That right there would've been grounds to break the adoption--if the allegations of psychological abuse had been adequately investigated. In contrast, we had no reason to suspect Kotan would do that sort of thing to Rugal.
(Even though it's not canon and I therefore do not count this in the debate, it's quite interesting to note that Una depicts Kotan as unconditionally loving despite the fact that HE is on the end of the verbal abuse all the time.)
A far more thorough investigation of Proka's AND Kotan's abilities to be fit parents is something I would've ordered if I'd been in charge of adjudicating this case, make no mistake. If any evidence showed up that Kotan was going to be an abusive parent, I would look for other options. If the verbal abuse Proka was suggested to have committed were proven, this would also be a factor I would take into account.
If Sisko and Starfleet failed, it was for lack of thoroughness in their investigation and for not providing incontrovertible evidence to back up their decision. And if you go strictly by canon, it COULD have turned in a direction where said evidence could appear. It could also have turned the other way where the Bajoran adoption should have been left alone. But since we don't know what the results of that investigation would have been--I'm going to come down on the side of parental rights.