I believe there are several interconnected reasons why people hate or resent those that have helped them the most.

• By helping others, we create an immediate disparity between the giver and the receiver. When the giver is known to the receiver, it creates a sense of shame or inadequacy in the receiver. It is not a rational response that is cognitively chosen by the receiver. The receiver is sometimes not even consciously aware of this new disparity. Whenever the reciever is in the presence of the giver, they feel inadequate that they were so dependant on the help of another and this sense of shame persists until the psychological debt can be equalised.
• When the giver is not known, such as in anonymous charity, far less shame will be created since the benefactor is unknown.
• This state of inequality is anathema to the human condition. Our psyche cannot withstand the powerlessness created by this disparity of status - both socially or amongst our peers.
• Furthermore, the sense of shame that the self feels in recieving under these circumstances is exceptionally painful. Briefly stated, shame is the human emotion linked to a disruption of purpose. Powerlessness is therefore a great source of shame.
• Now, ordinarily in the course of events, our psychological debts and credits with others can be constantly brought near equilibrium by the ordinary give and take of everyday life. We naturally understand the need to reciprocate meals, gifts, invitations and social niceties. This is not just done to smooth our social interactions but also serves to balance our psychological "shame" debts.
• Observe the behaviour of someone dodging their creditors. Are they avoiding them just to avoid making another excuse ? Or is the shame of dealing with the disparity in status too difficult to handle. This bears some thought.
• Now, imagine a person in incredible psychological debt to another. A debt which can never really be repaid. This means that the disparity and therefore the shame has no release valve.
• The receiver now exists in a state of cognitive dissonance. They are aware that they have lost power while at the same time their psyche needs to be powerful and shame free.
• In order to reduce the pain of this dissonance, the receiver may choose to vilify or denigrate the giver. By lowering the status of the giver, the receiver can reduce their sense of shame and recover a sense of self.
• However, this is not a guarateed or desirable outcome. A healthier personality will develop other techniques to live with this dissonance. Some people may grow their capacity for gratitude and find that the act of gratitude itself is a catharsis for shame. Since gratitude connects the reciever to the giver, this will lessen the sense of shame caused by the initial act of recieving. Positive self regard allows the reciever to seek opportunities to benefit the giver by staving off a sense of humiliation by using an innate sense of self-worth.
• This topic introduces a lot of ideas that need further explanation, but this is a fair overview.