I feel exactly the same way.
I really like Smart a lot, and I have always liked guys like him who work hard, play hard, and give it their 110% every night. I really appreciate that, which is why I've always been a (seemingly one of the few) big supporter of Avery Bradley.
But if the opportunity arises to grab a fish as big a Melo, and it takes including Smart in a trade to do that, then sorry kid but I have to let you go.
There is honestly nobody from the 2014 draft that I WOULDN'T trade for Melo with the exception of Wiggins, and even then I'd have to think long and hard about it.
Even from this year's draft - I would trade anybody not named 'Towns' or and 'Porzingis' if it meant getting Melo.
Getting a superstar is hard. Doesn't matter if it's through trades, through free agency, or through the draft, getting a superstar is REALLY hard.
Hell, even getting a 30 year old Superstar is hard. You need to work your butt off to build the right assets, and you also need a good portion of luck to go with it. Ainge knows how lucky he was to get a 30 year old Ray and KG here in 08.
Smart is a nice player, but he's not even a starter right now and while he might become a star, he may just as easily become a bust. He's an unknown at the end of the day, and if giving him up means bringing back a legit superstar, then IMHO you have to do it.
It would be painful to do, but you just can't say no to that.