Some folks see to have appointed themselves arbitor of what is appropriate to do on ones own land. They need to put their judgement of others in a box and close the lid.
have you considered that he doesn't actually want the animals but does not know how to do the down sizing himself. Sometimes people deal with a problem by ignoring it.
As that it is now your problem too, maybe go into solutions mode and find new homes for the mob?
Depend on where you are.
If you live in an active sheep and cattle farming region like I do, varmints are fair game at all times. If a coyote is passing through, we call the next ranch were it is headed, and one hears shots up the valley until he is ended.
One rancher's sheep dog went...
1. He was there first. Its up to you to find some accommodation. Put your preconceived notions aside for a minute, and stop assuming his is an irredeemable horror show. Breath.
2. Drop off a "Hi, I'm your new neighbor" box with baked goods, maybe some jam and a good sized bottle of whisky...