Have you kept any photos or details regarding this (ie dates, places, etc)? or been in contact with either
Dorset Badger Group (click on their name for a link to their website) or a similar group in Wiltshire?
I'm a member of the Dorset Group and I've heard of this happening in the County.
Dorset Badger Group have a person who records any roadside kills (see the Road Traffic Accidents page on the site) where you can fill in a form to send to them. On this form you can say whether you think it was in fact an accident or on purpose, or you can give them a ring (there is a phone number on there).
I know that in Dorset we take this sort of problem VERY seriously and the Badger Group are in regular contact with the Police Wildlife Liaison Officer.
I hope this helps.