Argh. Hit post. Anyway, you get the idea. It’s just so hard.
And it’s part of why I’ve been so pushy about trying to convince XaMcQ to speak to this owner. Maybe she’ll be one of the few who “get it”. Maybe she’ll take her dogs and train them up right. Maybe, if they’re really beyond hope, she’ll see it and have them destroyed before they become a problem.
Sure, it’s a lot of “Maybe”. But it’s a whole bunch of “No” if she’s not informed.
You are correct in thinking that sooner or later someone is going to get bitten. It may well be the owner. Someone most definitely needs to inform the owner, in no uncertain terms, of the risks that exist in dealing with what sounds like a very aggressive, out-of-control dog, no matter what the breed. This isn’t going to end well, for either the owner or the dog, I’m afraid.
I live in a city that has a pit bull ban. It’s silly, irresponsible dog owners will just get another dog and not take the time to train it properly. A ill-mannered and aggressive rotti can do damage too 
I do have some breeds I would prefer not to own, just my preference, but I when I worked at a pet store and would explain to people about rottis or chows I would always use the same comparision -
“if you are going to get a larger breed, potentially aggressive dog you need to invest the time and money in training them properly, a chihuahua that attacks someone may chew their ankle a little, a chow could kill a child. It’s just common sense.”
As per the OP, good for you, don’t let anyone bully you into a situation you feel is unsafe, giving your training and experience you know what was really going on, unlike the owner that may be in court in a few years saying “But my dog has never bitten or show aggression before.”
I live in Toronto, too, and I agree completely with this.
My take: it honestly doesn’t matter if you’ve got a teacup Chihuahua or a 80-pound Rottweiler. If a dog is growling/barking/snarling aggressively, acting like he might bite or flip out of control, you’ve got a very, very big problem. All dogs need to be trained to deal respectfully with their humans.
May I suggest that you put your impressions down in writing and either email or snail mail them to the owner? Keep a copy for youself too, just in case you’re ever called as a witness if the dogs attack someone. Lay out everything you’ve said here, calmly and concisely. If the owner has something in front of them that they can read when everyone is calm, it might make a much stronger and clearer impression.