You should purify your intention to Allah. if you are learning to be able to reply to his false allegations, this is permissible.
But if you are learning simply to debate with him even if you were wrong so that you would win, this is completely unacceptable and it is forbidden.
Having said that, you shouldn’t let this deter you from acquiring knowledge. You should learn so that you would know what pleases Allah and what would benefit you in this life and in the hereafter.