"I question the viability of a Catholic community which devotes any great energy to the question of ascending the throne while the born sleep in cardboard boxes on the streets and the pre-born are ripped from their mothers' wombs to be discarded as surgical waste" -
Quite. The Act of Settlement does not matter. It's another of the all too many hot buttons concerning civics and religion which fester in the more fetid, danker, darker corners of the land where the Jumblies live, for sure; but those who protest it seem to forget that the Act of Settlement is one of the most important documents in the British constitution.
Destroy the Act of Settlement, and you are over two-thirds of the way to destroying the Union. Whether independence would be a good thing for Scotland's Catholics is a matter over which I have grave reservations.