This is a little long, but I hope you bear with me. I definitely agree with those who say:
do not give him treats to win his affection!
It will not work. Your son is obviously very attached to you, is it because you give him treats? Of course not, and that will not help with his relationship with your husband either.
If your husband has always found quality time to spend with your son, and has helped in caring for him so that your son trusts him, then I would suggest that it is a phase or a control issue or both. I can understand that it must be very painful for your husband to hear those things, but I also agree with those who say that the more attention you have been giving the issue, the more it likely encourages your son to continue to behave that way. He is in control. Kids like to be in control. You might try giving him more control in other limited areas, while playing down the problem between him and daddy.
Try to give him more simple choices (that are still in your control) such as, "would you like to wear the green shirt or the blue?" "Would you like broccoli today or carrots?" "Should we walk to the park today, or to the store?" Don't ask "where do you want to go," "What do you want to eat" because then he'll likely say he wants to go to Disney land and eat cookies. Obviously that doesn't work.
At the same time, do not bribe him for his affection. Your husband should treat him the same as he always has (assuming he has always spent time with him and cared for him) and when he says hurtful things, tell him that you don't speak like that in your family. Tell him he can say whatever he likes in his room, but you and Daddy don't like to hear those things. If he won't go to his room, put him there, with the promise that when he speaks nicely he can come out. That way you're not trying to control what he says, only where he says it. He will soon learn that if he wants to be in company with people he likes and loves, he will speak kinder and more appropriately. Then it will be his decision, based on a real life consequence, because if you think about it, if you were to go around saying things like that to people, you wouldn't be in their company long either.
Hope this helps!