What i've seen from the video the spectator(s) did nothing wrong.
A rider, I think it was Van Hummel, touched the back wheel of another rider and fell down. Other riders tried to evade the falling rider and went into the dirt on the sides, where the spectators were watching.
One of them, I think it was Roelandts, bumped into one of the spectators, but she (as everyone says it was a woman) was not standing that close to the road at all, she was standing in the middle of the dirt. Well away from the road.
It's an unfortunate accident but not at all caused by spectators.
That being said, it might be better to push the spectators back a little bit further in stages with flat final 10 kilometers. Because the speeds get very high and the riders need some room to evade the inevitable crashes.