Our lurcher Gwyn has been to several festivals (including several Towerseys and Sidmouths).

Why do we bring her? Simply because she is far happier with us on a festival site than she is in kennels. No dog wears its heart on its sleeve more than a lurcher, and she shows every sign of thoroughly enjoying herself. We wouldn't bring her if she didn't. She is, though, an experienced border morris dog, and so is very comfortable in new situations and in travelling around with music and general merriment going on around her.

It ain't rocket science, and I'm not saying we're perfect or holier-than-thou: but we do take the responsibility (to other people and to her) seriously. Nobody else should ever have their enjoyment of the event impinged upon by the fact that we have Gwyn with us.
We keep her on the lead whenever around the site and wouldn't dream of letting her run around on-site off the lead, keep her well-exercised away from the site, avoid crowded and food areas, keep a weather eye out for children, nervous-looking adults, and other dogs, keep her off the seats, and make sure we clear up after her.

Nobody has ever complained to us about her or about her presence, and we would take the complaint seriously if anyone did. The biggest problem we have ever had was in getting across the Towersey site quickly when late for a concert, as far too many people (including lots of stewards!) wanted to stop us to say hello to her ...

It's about respecting other people, taking account of the fact that not everyone is comfortable around dogs, and just being sensible.
In fact it's what we do every day as (hopefully) responsible dog owners.

I would suspect that the dogs, and dog-owners, which cause problems at festivals are the dogs and dog-owners which cause problems the rest of the year round!