He couldn't bare looking into his little brother's face as he held his flaming sword to him. He may have been ordered to do this by his Father but that doesn't mean he has to like it. Everyone praises him for his obedience except Lucifer. Lucifer wants him to believe in himself, in them, but he can't. He can't believe in something against his Father's wishes, even if it is Lucifer as Lucifer has always been much too prideful. He can't bear to look into his little Luci's eyes as he casts him from Heaven. He can't bear to see the prideful defiance in his eyes. He can't bear it. He can bear casting his own brother out of Heaven for his own good, like a long, hot timeout, but he really can't see Lucifer's face while doing it. He can't watch his brother be in pain, even if he is the one causing it, the one who could stop it. He can't. He just can't.