Complex sentence: Schwartz argued that this type of activity violated the Objectivist moral principle of sanction, both because LFB was an explicitly libertarian organization and because it promoted books, such as The Passion of Ayn Rand, which Schwartz interpreted as hostile and defamatory towards Ayn Rand and Objectivism.
Split into simpler sentences: Schwartz argued that this type of activity violated the Objectivist moral principle of sanction. What's more, LFB was objectionable because it promoted books, such as The Passion of Ayn Rand that Schwartz maintained were hostile and defamatory towards Ayn Rand and Objectivism.