In the American South where I teach, the question comes up much less frequently, I expect, than in your part of the world. But yes, there are certainly a few people here, including the occasional student, who claim to be practicing “pagans”.
Obviously, the first question to ask is what exactly your interlocutors mean by “paganism”. For some it seems to be primarily a word of protest, signaling their rejection of all “institutional religions”, especially Christianity, and often accompanied by a smoldering resentment of “patriarchy”. On the other hand, the term may be used in a somewhat more learned and politically neutral manner to refer to the spiritual doctrines and practices of pre-Christian Europe, ranging from the Greco-Roman “mystery religions” through their medieval and early modern successors and parallels—doctrines and practices which, it is often claimed, were more attuned to the Divine Immanence than are those of their Abrahamic counterparts.
Given the context in which the question arose, my guess is that your inquirers are using the term in the second sense and that they may well be spiritually serious people who are searching for a genuine Path. If I were in your shoes, I think I would therefore begin by discussing the fact that religions have life cycles. While there are good reasons to think that the ancient Greek and Roman religions—those at least for which we have any historical record—were already in a decadent or degenerate state, I would be prepared to concede that in their own day they may well have been no less spiritually efficacious than Orthodox Christianity is in ours, and I would readily grant that the same might be said for the religion of the people (to take just one example) who constructed Stonehenge.
The problem, of course, is that these considerations are all quite beside the point from an initiatic or operative point of view. We can read about these religions in books, we can study their scriptural and archeological traces, and we can try to reconstruct what their theurgical rites might have looked like. But not being apostles or masters of the traditions in question, there’s no way for us to establish the necessary sacramental links to the originating revelation. Let’s just say—putting the matter in the best possible light—that contemporary paganism is in fact a distant reflection or last vestige of a truly valid religion. So what? Without an unbroken spiritual connection to this past, based upon the pagan equivalent of a silsilah or some other bona fide proof of initiatic filiation, the whole question is moot.
Let me repeat: I’ve no doubt that some of those who call themselves “pagans” are sincere and serious people. Others are clearly just in it for the novelty and exotic flavor, if not for the “protest” that I mentioned above, and others still may well have entered into contact (whether they realize it or not) with demonic agencies, and if so they are operating in a very dangerous state of spiritual delusion. One advantage of beginning your conversation with a discussion of this whole question of “apostolic succession” is that it should help you determine in which category your interlocutors fall. For anyone who is truly serious about the spiritual life will understand in his very bones the importance of sacramental continuity in the “production” of saints. And what’s the point of religion, any religion, apart from sanctity?