People who are introduced to the sport, should have the safety drummed into them.
People who are not new, should know better...most of it is common sense after all.
ANYBODY, who does something that could be deemed unsafe, should BE TOLD.
Nobody should feel that they cannot say something, even if you request a fellow shooter to come with you while you explain your grievance.
There are nice ways to say things, for minor infractions and there are firm ways to say things, for major infractions...without starting a row.
If the offender gets arsey, a word with the ground or shoot owner should help, as they will not want an accident and I feel sure would be very happy to convey their feelings to the offender and escort them from the ground if need be.