IMO, the issue is purely down to their strength and ability to kill a person.
I don’t doubt their temperament is fine, but when an animal has that much power they’re a serious danger in the rare situation that they’re out of control.
I like Jack Russells, I’ve got two, if they were strong dogs and someone said they’re being banned because of it then I wouldn’t mind. Just don’t let them breed any more.
A dog’s a dog. While I have a preference, ultimately I don’t really care what breed I have.
Pugs should be banned as well. A dog’s a dog, not a fashion accessory.