I don't think most "self-proclaimed liberal secularists" would have any problem addressing the Dalai Lama as "His Holiness", nor the Pope, nor the Archbishop of Canterbury. Being a "liberal secularist" doesn't mean you renounce all forms of religious or spiritual belief - it just means you try to treat them all with equal respect, rather than giving preference to one above all the others. So there's no inconsistency in showing respect and deference to the spiritual head of any particular religious group. I come from a Christian background - two ministers in the family at present, and my grandfather was a Bishop - and I consider myself a "liberal secularist", and if the Dalai Lama walked into the room right now I would have no hesitation in addressing him as "Your Holiness". And I would show equal respect to the the Rabbi and the Imam and the Cardinal who accompanied him. On the other hand, if a "self-proclaimed atheist" referred to any of the above as "His Holiness" then you might have cause for scepticism.
Well said.