An old man whose son had just been killed kicked mud on me when I took his picture. When members of his family heard about this, they insisted I come to dinner at their house. And they didn't have enough food for themselves. On the streets of my town, the Big Apple, I take abuse all the time. There are no hard and fast rules about what cameras to use.
Most photographers choose to work on the streets with a small, quick handling camera.
The Leica is perhaps the most popular choice, but hardly the only one. There is an understandable tendency to want to use a camera with auto exposure and auto focusing in the belief that it will help you work quickly. It depends on how quick you want to be. Manually presetting both the exposure and focus allows you to minimize the time the camera is at the eye. Camera up, shoot, camera down.