You're confusing two different issues. The first is whether it makes sense to see a Jewish right of return pre-Israel as justified, while seeing a Palestinian right of return now as not. Clearly it doesn't make sense. The second question is whether a right of return for the Palestinians today is just. I'd say equally clearly no.
I'd say you'd need to draw a false analogy with the Polish/German, Polish/Belorussian etc. situations for that. *Lunatic*, n. One whose delusions are out of fashion.