... What's fascinating is the link between Burns Suppers and the church. Ever since the first Supper was held in 1802, the clergy have been distinguishing themselves as Addressers of the Haggis, Toasters to the Lassies and Proposers of the Immortal Memory.
All of which is strikingly odd, considering Burns's attitude to the Church. His personal religion, if he had one, consisted of smatterings of Deism picked up in Ayrshire pubs and Edinburgh salons. There was a God, but having set the universe going he had then gone off like an absentee landlord, leaving it to look after itself. By contast, the Presbyterian God was a meddler, and judgemental, and Burns lost no opportunity to ridicule him and his followers. ...
How did it come about, then, that the clergy became such assiduous patrons of Burns Suppers? The short answer is that in the Kirk of Burns's day there were two churches, Evangelical and Moderate, and the Bard's sympathies were decidedly with the latter. There is a striking paradox here. The Moderates were patronised by the landlords; the Evangelicals were the sons and daughters of the soil, and blighted with what moderates and landlords saw as humble circumstances, conviction-religion and the fatal flaw of enthusiasm. In the light of A man's a man for a' that, you'd have expected Burns to favour the religion of his fellow ploughmen, but he didn't. Flattered by Ayrshire's Moderate clergy and Edinburgh's literati, he used his genius to satirise popular religion. An earnest Presbyterian was not 'a man, for a' that'.
And so, while Evangelicals gave Burns Suppers a wide berth, Moderates endorsed them warmly.
- from Donald Macleod's Footnotes column, West Highland Free Press, 30 January 2015.
(He also describes why many people think the Burns Supper structure is a parody of a Presbyterian communion service (as well as possibly having elements reflecting Freemasonry rituals, Burns having been a member).)