Why are the animals uneasy about Napoleon’s dealing with Mr. Whymper?

The animals were uncomfortable with dealing with humans. They remembered the first meeting after Jones' expulsion, during which, it was agreed that interaction with humans was forbidden.

Once again the animals were conscious of a vague uneasiness. Never to have any dealings with human beings, never to engage in trade, never to make use of money–had not these been among the earliest resolutions passed at that first triumphant Meeting after Jones was expelled? All the animals remembered passing such resolutions: or at least they thought that they remembered it.