“Anti-knowledge”? We already have a word for that – “ignorance.” Anyway, “anti-knowledge” would not be the unknowing or unknown but instead the knowing-to-be-false or known-to-be-false. “Anti-”, “contra-”, “counter-”, and “dis-” have that sense of a diametrical opposite rather than of simple negation. Like the difference between counterfactual and nonfactual. Or between disbelief and unbelief. (Sometimes in English “un-” works like “dis-” or “anti-,” e.g. “unhappy” which means a negative feeling, not merely “non-happy.”)