I also have sympathy for Williams. Rural crime police are under-resourced and victims are often frustrated by the lack of protection. However, the man he assaulted was a 72 year old walking a cockerpoo (not exactly the dog of choice for poachers or people with violent intent). That he mistook him for a lamper suggests he was so consumed with rage that he must be considered a danger to society, hence the sentence.
Does Amesbury’s light sentence suggest that some are treated more leniently than others? Of course. There are even more high profile examples who have got away scot free. Disgusting but we all know it to be true.