Man neighbors suck sometimes. Opinions?

I as a rule generally don't talk to neighbors, and mind my own business hoping they do the same.
So awhile back a house went up for sale across the street, and the first day they are there I see a large pit-bull in my front yard.
I step out the door with my friend's Mr.Smith and Mr.Wesson and the people are outside in their front yard.
The dog seemed fine, wagging his tail and lowering his head as he approached me, so I perceive no threat from him.
I ask, "HEY, is this your dog?" and the guy replies "Yea, he's fine."
I said "Uh, actually your dog in my yard isn't fine" so he calls the dog and it goes back across the street.
I personally HATE that (your property is community property mentality) and won't put up with it, or the next thing you know someone's kids are playing in your cars.
A week or so later the guy tells me the dog actually belongs to his son who is currently in prison and is getting out soon so I should meet him.
I told the guy I didn't have any interest in meeting his son, and he says his son didn't really do anything wrong but the way the laws are he got shafted and went to prison.
Stupid me I asked what happened and he say's it was consensual and the girl was not actually a child but 14.
It was obviously going to be pointless to mention 14 isn't consensual.

At that point I'm biting my tongue, because it's becoming real obvious that the Dad see's things the same way the Son did that got him put in prison.
Turns out the Son was put in prison for statutory rape of a minor, and he's in his early 30's.
Of course before all this we got a flyer on our door about a sexual offender living across the street, and I think the Dad wanted to try and explain to the neighbors why.

Anyway, it turns out the guy is one of those people I don't want **** to do with anyway, and besides the whole prison thing I chalk that up to me being somewhat like Eastwood in Gran Torino.
(leave me and mine alone and mind your own damn business)

To the point of this post, they let the pit wander the local neighborhood unattended.
We do have leash laws, but they ignore that completely saying "He's a good dog."

I try to mind my own damn business just as I ask of others, but you see where my dilemma is on the dog being anywhere at any given time around the house and yard, cars and family including two year old twin Grand kids.
Our back yard is fenced, but the front where our cars are is not.
I don't want to report them really, possibly adding to the problems the guy already has, but dammit it's a loose pit for one, on my property at any given time for another, AND there is a law about loose animals.

What would you do?
If I go and try to explain the concerns to him he'll come off with some attitude and excuse why it's fine and I'll end up going to jail for knocking his *** out. (I hear his attitude all the time, and it's definitely a prison attitude) and he is one of those puffy chested ignorant little pricks with Respect tattooed on his neck.
The Dog didn't do anything wrong but just be a normal acting friendly dog.
Calling and reporting it would probably just end up being an everlasting fiasco with the Father and Son both since they both seem to think the same way.

Opinions?
I have a suggestion....

Call a Pit Bull rescue organization near you and tell them about the dog. Tell them it's a nice dog, but runs free all the time and you think it's being mistreated.

I can almost guarantee that someone will swoop up the dog and find a new home for it.

I've dealt with dog rescue organizations before. The people involved can be very aggressive about getting the dog off the street and into a home where it will be taken care of.