Pablo isn't a bad person, the hatred for him is mainly due to his performance and work ethic, or at least his eating habits.
Lackey is actually a douche, I've heard from numerous people who've met him he is a douche, and just the way he acts he's always come off as one to me as well, similar to Papelbon. Lackey used to yell at his teammates after errors and not in a "good" way, but in a "you f***ing suck" way. Which I didn't like at all, you don't do stuff like that. I don't think Pablo/Lackey are really comparable as people. But what it comes down to for both guys is performance. If a guy isn't performing, especially while being paid a lot, they aren't going to be very well liked by that fanbase.
Edit: This is a good article describing why he is a douche and why people disliked him.
http://www.overthemonster.com/2013/11/4/5065214/john-lackey-red-sox-hero-a-revisionist-history