Anything goes? Not really. Anything may go, but not at any point. There is a time and place for everything, and a season for everything under heaven, to paraphrase the Ecclesiast.
Ancient rhetoric was equipped with three notions of testing the appropriateness of any speech. These were kairos, decorum and the audience. I say ancient rhetoric, but actually these three categories apply today, and I suppose they will always have force as long as humans use speech (or written text) to accuse or defend, exhort or dissuade, praise or blame.
Kairos commands the right moment. It defines the proper time for action, the moment when words become crossbow bolts on the lips of the speaker. The best speech will fail if it’s delivered at the wrong moment. Timing is everything, as any successful speaker will tell you. A moment too early or too late, and the words will miss their target, falling on deaf or overexcited ears. Or on no ears at all.
Decorum measures the circumstances, looking more widely at what words are used, the values they embody, the ideas they promote. It also tracks the suitability of an idea in the wider context in which it is used. A decorous speech is not necessarily one made in good taste, modest, or comme-il-faut, but one which matches the expectations.
Finally, ‘audience’ is, well, about the kind of audience a speech is designed for. There is no speech without an audience, and a speech without an intended audience is like a rock drifting through space, lost in its own deluded inertia.
What’s the point of preaching if it’s to the choir or to the already converted?