I have five English Setters one of the friendliest dogs available, but I would not dream of taking any of them to a Festival.As already stated the conditions for dogs being left or taken into tents or kept in cars are not suitable.In general the music hurts their ears.Some breeds of dogs their car and tent becomes their territory so they guard it.A little child crawling into a tent with a dog in it is in danger.
I agree that some dog owners do not act in a responsible manner and properly clean up after their dogs.I think most of us have been to concerts where a dog has been left outside chained up and barking for it's owner.Many a good performance or live recording has been spoiled by a dog barking.Finally think about the poor dog ,where most of the audience is interested in the stage performance, many a poor dog has been tripped over. Finally a dog that is wonderful with humans can be a killer towards other dogs and many a dog fight is the result,with people being bitten trying to separate them.My thoughts on this subject is leave them at home or put them into a kennel.
Al