[Access]

"The incidents are believed to be the work of animals rights extremists."
I don't see any evidence of this, not from reading the article at least. IMO the quoted statement above is just pure conjecture. People assume things, but that doesn't mean it's true until it's proven... in the case of criminal acts, it must be proven beyond a reasonable doubt in a court of law.

The missing body could be the work of animals or just bad karma.

A 'petrol bomb' might simply be an exposed gas can of diesel fuel that someone forgot or inadvertently left lying around. For farm equipment or vehicles driven around a farm, you typically carry a container of some extra fuel in case you run out while in the fields. The container can fall off the tractor inadvertently or somesuch.

The threatening letters could be faked by the family in an attempt to stigmatize peaceful protesters.

The article mentioned no concrete evidence that it was done by 'animal rights extremists' or such, it's just shoddy reporting, nothing else.