Why is it dangerous? (Unless they're breaking the speed limit to make the light, obviously.) Just the risk that they might misjudge the timing and enter the intersection after the light turns red? But lights have a built in delay before turning green to account for that.
I think they question they were asking was: What is the fire upon which gasoline is being poured?
Given that, even if someone entered the intersection on yellow, they would be out of the intersection before perpendicular cars/bicycles/pedestrian signals turn green, how is it dangerous?
It seems the risk of collision is 0 as long as neither the driver nor the perpendicular cars/bicycles/pedestrians are illegally running red signals.
Because vehicles are often already traveling at or above the speed limit.
Just as the yellow light is intended as a "start slowing down" but is interpreted as "speed up to beat the light", the speed limit sign is intended as a "do not exceed this speed" but is interpreted as "you must be traveling this speed".
If we assumed that most vehicles are traveling the speed limit or faster, which is the case in my experience, then accelerating further is like pouring gasoline on a fire.