I agree with that to some extent. If Cho or the Blazers' front office has a bad relationship with the current Nuggets' front office, that could place a chill on any negotiations. I just don't think the "won't trade with a division rival" thing is generally a major factor, especially when a team is executing a rebuild trade.
Because Melo is a top 5 talent in the NBA. When he is on, which is often, he is an unstoppable scorer. But of much more importance to the team: He is a BIG NAME star player, he is from Brooklyn, where the team is building a new stadium that they need sell A LOT of very, very expensive seats to pay for. Without a big name draw they will have a hard time selling those seats. They failed to sign any of the big free agents this last summer, and they are pretty desperate. Harris is not the best match for Carmelo and is hurt a lot; Favors is raw and needs development and Brook Lopez is probably their best asset. They will do their best to improve the team and make Melo and their other good players happy. Other than that, why should they think too far ahead. Some Blazer fans were fitting the team for rings after winning the lottery and dreaming about pairing up a dominant big with an All-Star guard who was a great closer. How did that long range planning work out? Best thing is not to out-think yourself.