I wouldn't beat around the bush about it. A wishy washy approach often times gets no results. Wrong is wrong and right is right. I would be direct and up front about it. I'm not saying flip out and start yelling, but a direct calm approach will probably get the best results (if any). The real problem is that these types of people are well aware of what they are doing...How are they not? Yet they treat the animals like this anyway. It's sad...Good luck.