The non-religious (or very irreligious) usage nearly always has a negative innuendo regarding the speaker in question. It means to speak pompously or dogmatically about something and usually indicates the one speaking is doing so in a knowing, self-important way, especially when that person is not qualified to do so. Furthermore, used in this sense, the meaning includes the unspoken, eye-rolling message that the speaker also doesn’t know when to shut up and leave well enough alone.
An example of this meaning may be this short conversation. “There he is again; the town drunk lecturing the congregation for two hours on the evils of drink!” “Yes, well, that’s better than the circus fat lady taking all day to tell us all how easy it is to diet!”