Spoiler - alot of guys don't really learn know how to defend until they get to the NBA. Want me to name a bunch of bad defenders in college who developed into good NBA players/defenders after the age of 19? Development of your skills and body don't end when you get drafted.
Besides, no team in the NBA is more equipped to manage and compensate for a bad wing defender than the Celtics.
I'm talking myself into Dunn, if they feel he's the best prospect which is what most people and teams seemed to have settled on. I've always liked his game, but he's arguably the worst fit of any lottery talent for the Celtics.
Still - the roster doesn't have to be settled after this draft or even the season. I'd rather have a glut of guards/wings than big men. There are a lot of lineup possibilities with IT, Bradley, Smart, Crowder and Murray/Dunn/Hield. Smart can easily handle 3s - he locked down Korver before.
I'd prefer Bender though - the Pelton stats have me excited, although they generally seemed to love foreign players.