In my opinion? No, it's not wrong. Why?

Because I've done it. And after going through this same internal battle in my head for days, when the dog got out and ended up in my backyard, I took him in and called the ASPCA. And now, we adopted that dog. And he has a damn good life because he deserves all the love and care a human can give an animal, not the life he was getting. Which was disgusting and horrid...

Keeping an animal on your property under the suspicion of abuse is not something the SPCA or what have you is going to look too much into. If you have explanations and examples, like you gave us, they will write all of that information down. They will bring the animal in for an examination, etc, and more likely than not see exactly what you were reporting.

And honestly? It's SAFER for the animal. If you call the SPCA or any animal service for protection, the animal can face further abuse upon the owners finding out, abandonment, or death. I have heard it happen more than once, and I KNOW this would have been the future for one of our lovely dogs if I didn't follow my gut.

Follow your gut on this. You have to balance logic and reaction here. You're reacting as a protector. Why is this? Because you're seeing an animal being harmed. Why are you questioning these actions? Because you're wanting to follow through with them to keep this animal safe.

If the dog comes to your yard, you're not stealing anyway. Especially if you're calling protection for the dog RIGHT when it arrives.

You're a good person. I don't at all think that these actions are wrong, especially when it is from a protective instinct.

Good luck.