I can't say I dislike dogs themselves. I've had plenty of good experiences with my cousin's dog for example. However, what dogs are allowed to do in society is entirely unreasonable. At a park or a trail a stranger's dog might stick its nose anywhere it can reach on you or on your belongings. It might even sniff your crotch. It can also try to climb or hump your legs. Yes, it might be called normal but if you think about it without the "dogs are like that" prejudice, it's clearly a very unreasonable invasion of personal space. Imagine the criminal charges and newspaper articles if a person did that. So, why is it acceptable to have a person permit a dog to do that? Even wild animals don't!
When I'm with a person who finds this behaviour highly disturbing, that's even worse. Hearing someone I know and care about freaking out because of a dog is unpleasant. However, the dog owners in such situations often don't seem to care, and they sometimes even laugh about it.
Dog shit is another issue. Why is it reasonable for dogs to shit on a trail or sidewalk? Again, imagine if you saw a human doing it and note that even wild animals don't generally do that. Can't they do it somewhere humans don't walk all the time? The main problem here is the people who don't clean up after the dog. Nanaimo was the worst; based on what I've seen I could call it the dog shit capital of the world. However, most cities have plenty of dog shit lying around. That stuff is a pain to clean off shoes. Meanwhile, dog owners just get a small fine if they get caught, which is very unlikely. I've actually seen places where littering fines were higher than dog shit fines, which is totally unreasonable when you consider how much worse dog shit is than typical litter.
Dogs are even annoying with the noise they make. Some dogs which are stuck in yards can bark loudly for a very long time when someone's passing by on the street. It's pretty much the loudest sound one can hear in a residential area. Once again, the way it's tolerated seems quite unreasonable.
Perhaps the most important thing to note is that people have many other pets, and none are quite as annoying to strangers as dogs. Nothing else will regularly approach you while you're outside and bother you or make loud noises as you pass by. Some pets might bother you in someone's house, but that's different.