So basically, the Unicorns are the worst criminals in Equestrian History, seeing as how their Dome to control the Earth Ponies for their benefit had the potential to kill off the three races entirely through starvation. And to this day remains the biggest coverup that would shake the foundations of their whole society if the truth ever came to light. The Earth Ponies and Pegasi would turn on every Unicorn, there would be an uprising against Canterlot.
The Unicorns, by this explanation, are perhaps the worst criminals in Equestrian history. Their pompous nature to be held above the Earth Ponies at any cost almost brought upon genocide via starvation.
Panel 10 (Dark creature at the magicdomewall): However each cloud hat its silver lining. From the moment the dome appeared, the farms hadn't been attacked even once. Somehow all the dangerous creatures were repulsed by the barrier, while those within it were calmed down. What's good for one, can be a tragedy for another, as the pegasi were no lnger needed for protection. Thus there were no plans to share the crops with them. For two weeks now the sky-bound ponies were without food. Upon finding out that those who hat betrayed them were having their own taoubles, teh pegasus would only gloat, not immediately seeing the opportunity that this presented them.
"And then they offered to control the clouds? Control the rain and the snow, is that it?" "Winderfull, Sindy, thats exactly so!"
Panel 11 (Twilight and daughter sitting at table in train): "This arrangement, that came about in the first era, in the era of disharmony, continues to this day. But as you know, after the great winter, all the races of the ponies came together. And since that time we do what we do not for selfish reasons, but to help others." "Why then, wasn't this dome removed after the great winter?" "Well everyone simply forgot about it. It hat existed for so long that no one remembered how it was before; independent weather, automatic change of night to day. It seemed that it's been under the control of the ponies forever." "Wait a moment, then how do you know all about it?" "I am the number one student of Princess Celestia after all, remeber?" said Twilight with a wink. Then, story finished, began to gether up their books. The long journey was over, and the train was already coming up the station.