The video below starts in the middle of a side-story where Valzeride (the antagonist and hero of Silverio Vendetta) confronts Gilbert over his ideals.  They begin to fight because their ideals, while both based on goodness and light, are inherently opposed.  Valzeride ultimately sees himself as inhuman garbage and strives to slay evil and bring happiness to the people of Adler, whereas Gilbert wishes to create a world where people like Valzeride are free of jealousy and judgment of the masses.