As a dog owner who frequents a lot of west end parks, I actually try to pick up stray piles of steaming dung if I find them. It helps keep the parks clean for everyone. Not even dog owners like stepping in shit.
There are a ton of people that let their dogs off leash outside of the leash free areas, and they should be ticketed. I walk along the lake toward the Humber Bridge, and I've met dog walking folks with their dogs off leash, asking me why I wouldn't let my dog go off leash. Well, geez. Maybe it's because its not an off leash area; the bikes, the kids, the cars in the parking lot. A little common sense. So I definitely feel for anyone that has experienced this.
However, there is a lot of dog owner hate that is a bit unwarranted when people start grouping all dog owners into the same irresponsible group of people. You're more likely to see a group of kids with their parents trashing a park place with their Tim Horton's cups, and candy wrappers than a dog walker without a bag.