Foreign aid, when all goes well, is a good thing.  The usual metaphor is of neighbors helping neighbors get through a bad patch.  International friendship, brotherhood of man, improving all of civilization...

That said, foreign aid does not invariably go well:

 1. it might be incompetent:
    
    * workers might be sent who are so poorly organized they make things worse, working at cross purposes to natives, or taking command, but
    so poorly that little is accomplished.
    
    * large sums squandered exporting domestic methods that can't possibly succeed in a different environment.
    
    * monies might be mismanaged by donor groups, who pass on only a small percentage to do the job at hand.
    
    * workers might spread disease, pollution, or import quarantined objects or creatures.
 2. It might be reckless and expedient:
    
    * Imports which help in the short term, but inadvertently
    bankrupt native business by indirect and unintentional competition.
     
    * Farming methods that do not scale.  
    
    * Useful machines that cannot be
    maintained without an infrastructure that won't exist for
    generations.
    
    * dangerous pesticides, parasites, invasive species...
 3. It might be insufferable:
    
    * Prideful missionaries distributing goods and inferential insults.
    
    * Well meaning volunteer youths, who can't speak the language, believe anything, and ooze pity.
    
    * A toxic bureaucracy or two.
 4. It might attract and import criminal elements:
    
    * Rogue volunteers, abusing the local comforts and customs, seducing and abandoning women and children.
    
    * Carpetbaggers who buy up the damaged local economy from temporarily distressed sellers, export the valuables and never
    reinvest locally. 
    
    * Dealers who import/export contraband goods, who do reinvest locally, in bribes and unhappy products.

 5. It might be corrupted by native criminals:
    
    * Resources might be diverted into a black market economy, or even exported.

There are schools of thought that argue foreign aid can be, and is, harmful in a more general sense: 

1. Aid is sometimes used as a kind of economic cold war weapon.  That is a small nation between warring empires, will be aided, abused, and advertised to whatever degree suits those empires' conflicting strategies.

2. [Some argue][1] that even sincere aid has been based on an impractical model, which prolongs those very conditions it's intended to assist.

Since Venezuela already regards itself as being abused by such efforts,  and holds the US as a direct cause of its food shortage, it therefore would look upon such aid as a further hazard, and disdains it for the same reasons children are taught to refuse candy from strangers in vans.


  [1]: https://en.wikipedia.org/wiki/Dambisa_Moyo#Dead_Aid