Markinabox,

no you were NOT out of line by stopping that operation.
You may have prevented a disaster with possible death from injuries due to thier incapacity to realize the danger they were creating by using the machine in such a manner. As for your boss blowing that off? He should be drawn and quarterd and have his nuts cut off by letting them to this. Trying to save a buck is a very poor excuse to put people in harms way like that... {sighs}

Even if the rigging company did have insurance your company could still suffer from the accident(if it had happened) due to not doing anything about it knowing it was going on.
Not to mention if OSHA had just happened by and seen that going on? I guess i dont have to mention the consequences that would come about if they get involved, they love BIG fines :)

Keep up the good work, save lives, stay healthy & safe :)