Need some advice PLEASE!

His parents have this chihuahua dog that has always just been a little shit. Mainly because he's super over protective of my SO mom. You can get ANYWHERE near her cause he starts freaking out and trying to bite. He's bitten people before, and they are actually lucky no one has tried to sue them or something because he's bitten strangers that are walking on the sidewalk. 

And he is little but his bites are mean!! He bit my father in law and left him a huge bruise and blood marks. 

Anyways, every time she gets the baby he's growling at the baby and barking. She was sitting with my daughter once (completely oblivious to her dog going nuts) and he jumped up and ALMOST got her leg. I was watching him closely and literally just in time pushed his face away from her. I am SO afraid of them letting an accident happen. And no one listens to me. I feel like he could realllly hurt her if he bit her! But I don't want to be rude because it's there house and when I do say something they disagree. He's super spoiled and they allow him to act that way. 

I know we are out of here soon, but it almost just happened AGAIN and when I ask if she can get the dog away or stand up with her so he can't get to her she just tells him, "down" and he does it okay 2 minutes later. 

I don't want to be rude and demand anything but my daughters safety is everything and I don't know how to go about it the right way considering they don't listen when I'm passive about it. :(