Sorry about your kid.
Hopefully everything is OK.
Don't want to start shit, but after reading the thread I feel like I should share my small experience with pitbulls.
When I started dating my fiancee (8 years ago) her family had a pitbull and I fucking hated it. I wasn't used to big dogs (my family always had mini pinschers), and I was really afraid of him.
The dog never gave me much attention (probably because I was around my then GF all the time when close to him) and eventually I lost most of my fear, but I still never got too close to him without someone from her family around.
3 years ago we decided to live together and moved to a big house. Since I'm away from home constantly she decided to get a dog for protection and bought a pittbull, his name is Thor. I didn't want a dog regardless of breed, I don't have time to deal with then or any kind of pet, but considering that she stayed home alone so much I ended up agreeing.
I asked her to buy a female since they are supposedly more calm but she couldn't get one and bought a male anyway which displeased me.
In the 3 years we have had him he never attacked anyone, including a pair of burglars who entered our house last year and took away some stuff. The dog is useless as a guarding dog, but at least he intimidates people with his looks and his bark...problem is he don't barks that much and as soon as he sees anyone, even strangers he just starts wiggling his tail and gets in a playful mood.
I never trained him (don't know how), or paid anyone to train him to be a guard dog or just to teach him to behave. My fiancee is the only one that takes care of him and she is really loving, she loves that fucking dog.
Our family is always visiting, including my sister and her kids. They fucking love the dog too since my sister won't allow then to have one (regardless of breed). At first my sis didn't want the kids around the dog, or even bring then here because of him.
Anecdotal I know, but it's just my experience. Animals aren't inherently bad, and they will usually leave you alone if unprovoked, unless trained to act otherwise. I hope this wasn't the case with you father-in-law dog.