Prince Blueblood, distant but traceable blood relative of Princess Celestia, lives as a tool of Equestrian society. He views his very existence as a debt he must pay, with few career options other than civil service. Fortunately, an attorney's duties suit him.
He believes in Equestrian society, for better or for worse. In his opinion, changelings rank among the "worse". So when the commander of the Wonderbolts accuses one of murdering Rainbow Dash, he sees his involvement as foreordained, especially once a Princess signs on to oppose him with revenge on her mind.
He is also widely seen as an extreme narcissist, only tolerated because of his link to Celestia. But many things are not as they seem.