Words of wisdom there TastingtheRainbow - I haven't read the whole thread but I can imagine there has been a lot of talk of Rotties being "dangerous dogs" which of course is not the case. It all depends on the owners and how the dog is treated, nothing to do with the breed.
However I totally agree that the OP should not visit with her young baby, while the dog is there. Yes the dog could be kept in a separate room but the mom is going to be on edge all the time, and that's just not fair. The other worrying thing is MIL's attitude - claiming the dog is all right around children. I would worry about anyone making a statement like this because as you say Rainbow any dog can bite and no dog should be trusted with a young baby.
I've just been looking at stuff on the internet my DGD has "liked" and there are loads and loads of pictures of babies with dogs, and it's all very cute, baby laughing at the dog's antics, but I am astonished at how parents let their dogs so close to sometimes very tiny babies.
I had two kittens when my son dil and grandchildren came to stay one time (and the baby was only 3 months old) and I assured them that I would ensure that the kittens would never get anywhere near the baby, especially her pram or cot, as it's well known cats like to jump in warm places and could suffocate a baby. My DIL was very relieved as she'd been worried about this, but she knew about the kittens.
We had a yellow lab when my first DGD was born and they visited often, but we never ever left the baby and dog in a room together when no one else was there. Labs and golden retrievers are notoriously soft, BUT I heard of a horrendous thing with a golden retriever (much loved family pet) who (without provocation) attacked the 11 year old boy of the family. He bit his lower jaw very badly and fortunately the neighbour was an off duty paramedic and was able to pack the jaw and get the boy to hospital or it could have been a lot worse. Apparently the vet said the dog must have had a "rogue gene" - so who knows.