I guess it would be similar to the endless debate on smoking. Smokers know smoking kills, but they do it anyway, they accept the risk and the shortening of their lives in exchange for it.
The same case here, there is definitely a risk in hand feeding rays, if people want to risk their health and well being, we have to respect what may seem stupid to us. WE may seem stupid to them not enjoying the interaction with such a wonderful animal and not embracing the risk.
It's all about perspectives and respecting differences.