What's your stance on "aggressive" dog breeds?

Ironically,the most aggressive dog I've ever met was my sister's Chihuahua until It learned to trust me.But a chihuahua is easily contained in the yard.

Some breeds like pitbull's or Rottweilers because of their body size & bite force need to be kept in a secure environment, just in case they do escape & get stirred up enough to latch onto someone

The real problem is the owners of those breeds. Like Cesar Millan says " there are no bad dogs just bad dog owners". I'm sure others will disagree but this is my opinion, and I think that is what you asked for. I have personally spent time with 9  or 10 different pit bulls in my life and never have felt threatened or even been nipped by one of them.

There are people who intentionally purchase tough dogs and then make them aggressive, but then there are some which have a tendency to be aggressive just based on the particular personality. While it is not fair that they all get thrown under the bus, or even that a nice dog can be made to become aggressive --- plenty of places do not want to deal with the potential liability, and just ban the dogs on their property. The risk may not be worth it, perhaps even for insurance liability reasons. Plenty of people want dogs to be somewhat aggressive, because they are looking for protection and to thwart off human attackers, not necessarily because they want their dog to get into dog fights with other dogs -- but nevertheless, the person is liable if their dog attacks a person.