Why can't I murder this drunk guy and why is he a target? (aka: Where do I find Duccio for the Bully Achievement?)
This guy is related to an acheivement.
http://www.trueachievements.com/a157188/bully-achievement.htm
Beat his face up. That's it. With your fists, I shall add.
Storyline wise, I think it's the ex husband of your sister, if I remember well.
I shall add his wiki page, for story's sake. http://assassinscreed.wikia.com/wiki/Duccio_de_Luca
This is Duccio, he appeared in the previous 2 AC games. He was Ezio's sister's fiancee but cheated on her. You can beat him up (fists) for an achievement/trophy (on the x360 and PS3, respectively), and he won't come back again