It is also possible that had the riders not been wearing helmets,their increased peripheral and hearing might have prevented this.
You might want to go back and read the original post again, this time reading for comprehension. First off there is no mention of helmet or no helmet at all in it.
Secondly this little bit here is more telling regarding the motorcyclists attention probabilities.
"There are four Bikers in front of me. One girl, three guys - all under 30. Light turns green, they wind up their bikes and start to cross into the intersection.
They are talking to each other (fatal mistake)."
Please note that the riders did not seem to have a problem TALKING while riding so therefore hearing would not likely be an issue. Perhaps if they had quiet pipes they might be able to hear something coming. That of course is a totally bogus assumption since again there is no mention of loud pipes in the original and follow up posts.
Perhaps if the drivers were paying attention to the task at hand they might have seen the threat. A simple side to side scan before entering the intersection is a good insurance policy no matter what you are driving, say like a car with the AC, radio and telephone on while yelling at the kids in the back seat much less a motorcycle.
Blaming the collision on the riders wearing helmets is like blaming the red light for not stopping the car. The equipment does not excuse the rider / driver's lack of attention or inability to follow the basic rules of the road. In this case there is also no mention that they WERE wearing helmets either. Perhaps if they were not wearing them the one dead at the scene might have been alive had one been worn.