As someone who doesn't have kids, by choice, but who DOES work in a very large children's museum - I heart them. Sure there are pros and cons to them. There are also pros and cons to letting your "runner" loose in a VERY crowded area. Can they get hurt because some bozo clotheslines them? Yes. Can they get hurt running around and tripping over a curb? Yes. Can the tether be abused? Yes. Can a non-observant parent cause a child to hurt themselves b/c they aren't paying attention? Yup. Anything can happen - it depends on you and your child and what other people think is not your concern.
I do resent the they-make-your-child-look-like-a-pet arguements. I love my dog as my child and I keep him on a leash when I need to BECAUSE I love him. He goes off leash when it's safe. There is no difference. You are responsible for the safety of your child and I am responsible for the safety of my pet. How WE as the parent/owner decide to do that is our business and no one else's.
You might get dirty looks, but I wish you strength and luck! Don't worry about what other folks think!