I think hate is too strong a word. To be honest, there are worse characters in the game that you can hate as they have been in previous GTA's and I don't think I have ever really hated any character.
What I don't like about Jimmy isn't anything to do with him individually but about Michael's family as a whole. That they blame Michael for everything and are unrepentant regarding their own actions. Jimmy tries selling Michael's boat behind his back and it's Michael's fault. Tracey essentially whores herself to try and get famous and she then says that Michael has ruined her life when he stops her. Amanda sleeps around and, again, it's Michael's fault. Now, Michael is no saint but not everything can be pinned on him. But they do so anyway. I find that attitude annoying.
The key word there is annoying. Because for the most part I find them fun to be around.
I think you touch on good points. Hate is a strong word, BUT I believe that the intent of the writers is that we were supposed to dislike Jimmy in the story for all the reasons you delineated.
Its the mark of a good story when it creates such controversy and debate. Writers WANT you to be emotionally attached to their stories. They want you to really like certain characters, dislike some, and hate others, at least insofar as while you are immersed in the movie, book, show, or game.
You aren't supposed to LOVE every character, nor do writers want us to be emotionally neutral about them.