I wouldn't want to go in, but at end of season when there's no general public sessions and everything is thoroughly cleaned out before the next season, it's not going to affect the general public.
I wouldn't have thought that the dog hair shed would be much good for the filtration systems though.
I swim at a managed lake for water sports. I'm clearly no germaphobe when I'm opting to swim with geese, swans and all the other wildlife on site, but when I had a rest in the shallows recently, the oily film of dog hair that accumulated near the entry point was rather gross. Fortunately the dogs don't tend to swim out very far to affect the rest of the lake and it's only a limited zone that they affect.
TBH I'd rather dogs weren't there or at least had a seperate zone out of the way. It's annoying trying to access the exit point trying to work out how to swim past a hyper excited dog playing ball. There are often reminders to dog owners about not obstructing the area.