I've caught sting rays while fishing when I lived in Florida. After the first one, I started doing a little research on them to learn how to avoid getting hurt by one. It seems that only the barb that is halfway down their tail is the only dangerous part and they only use it in self defense if something starts to hurt them, such as someone walking through salt water and accidentally stepping on it's fin, or a shark biting a chunk out of it. It mentioned that if you drag your feet as you walk when you are in salt water, then you won't step on it, but instead just bump it causing it to quickly swim away without swinging its barb at your feet.

It goes on to talk about the opportunity to swim with sting rays at Disney island resorts. The staff there will trim the barbs to make them harmless. No this is not animal torture because the barb is similar to human finger nails. It will grow back and they just trim it again.