What a frustrating situation. Dogs can take you down and cause you to suffer injuries that take months to heal and many dollars to pay for.
You have to protect yourself. Talk to people. Know your local laws. Collect phone numbers. Record information.
Some of my most enjoyable bike rides have been interrupted by pesty dogs that chase and get close to my wheels.
Two summers ago, I spoke with a woman about her Rottie that chased me and scared me. She said that the dog had also been chasing motorcycles and she'd had enough of it. She said that she would shoot the dog and she DID!! Drastic, but end of problem.
I am involved in the local Humane Society and Animal Shelter. I get frustrated because I still see pit bulls in our county. People ignore the laws if laws regarding dogs even exist around here.
There must be communities that support bicyclists' rights to be free of chasing/attacking dogs. Sure wish they could influence the rest so we could ride without fear.
Stay safe.
Barb