Greensleeves, that's a little harsh saying people who keep dangerous dogs are twisted or dim.
I am neither, but there are people on my estate who class my two dogs as dangerous. Not because they are people aggressive but because they are occasionally dog aggressive. It varies from dog to dog, and who has yelled at them first.
My Dalmatian was dumped at the rescue centre for 'attacking' a 10yr girl who took it into her head to climb over the garden fence where he'd been shut in for over a year. No blood was drawn, he simply bowled her over with sheer enthusiasm. Despite this, he is the most gentle and easy-going dog round the house, to the point where my 7yr old can sit on him, and he doesn't flinch. He was also bitten very badly as a puppy, and I suspect this may contribute to his problem he has with other dogs. It's just random dogs in the park he's unsure about.
I've had the Dal for over 2.5 years now, he is fitter than he's ever been in his life, and we are constantly working on his dog aggression. But because I do not trust him, he is never allowed off the lead at any point in time. I cannot guarantee that he'll not behave.
The Jack is also a rescue dog, from the same centre, but he's all mouth and no bite (partly cos he has next to no teeth left). His 'aggression' comes from recognising how uncomfortable the Dal is when other dogs come barrelling up to him, so he tends to guard the Dal, and chase off the other dog. He does this with dogs that know the Dal, let alone strange dogs. I can, however call him back immediately, regardless of the situation.
I walk my dogs to the school every now and again, and I am continuously frustrated by the 3 or 4 parents out of the hundreds there who find offence to me walking through the park in front of them on the way to school, or complain to the school about me tying the dogs up 5 yards away from the gates (how dare I?!) yet herd their kids in a wide berth round them as though they are at full stretch on the lead, lunging at all and sundry walking past. They are not. They are usually stood or sat quietly, more bothered about sniffing the bushes nearby than the 300 kids filing out of the gates. If anyone has a problem with my dogs, I'd much rather they come up to me and tell me rather than leave it to the dragon on reception to grumble at me.
I do like it however, when I get some lovely children coming up, with their parents, asking if it's ok to pet the dogs. This shows respect and the dogs enjoy it too.
I agree with the OP's concern however. They can be intimidating, and I can appreciate how the situation must have distressed the OP. I do think you should have a chat with the owner though. Speaking from an owner's perspective, I think they'd appreciate it better rather than a hammering on the door from the local police.