How to distinguish between "blasphemy" and "sacrilege" in a non-religious context?

In religious context, a sacrilege is an action that disrespects the fundamental beliefs or traditions of the Church; for example, putting out ghoulish Halloween decorations for Christmas, or otherwise mocking or disrespecting the religion through actions.

Blasphemy is similar, but it connotes speech; blaspheming is saying something unclean, insulting or disrespectful to God or in his presence; cursing in church and talking to the sky with a "bring it on" attitude are traditional examples of blasphemy.

The term that probably best describes what you did is "heresy", which is to express thought or belief that is contrary to church doctrine. By saying that sweet peppers can be mixed with hot peppers to tame the heat of chili, you contradict the beliefs of chili "fundamentalists" who think that only various hot peppers (and derived ingredients like chili powder) should be added to chili. To actually do what you have said would be sacrilege.

The terms are similar. Blasphemy often refers to speech, while sacrilege often refers to a destructive or undignified act.

In a joking context, you might say that the suggestion itself to use a mixture of peppers is blasphemy (it's irreverent speech), whereas the act of mixing the peppers might better be described as sacrilege (you're mistreating something sacred to the chefs).

I don't think most speakers would make a strong distinction between these uses, and the terms have a history of being used interchangeably.

To blaspheme is to fail to show respect to a religious notion. While you could engage in a symbolic act of blasphemy, the fault is usually a verbal one. A case in point would be author Salman Rushdie's Satanic Verses, which was not deemed sufficiently deferential to the Islamic prophet Mohammed. Similar to heresy.

To commit sacrilege is to desecrate the sacred or holy. This would more strongly be a physical act, rather than a verbal one. Say, the kicking over of tombstones in a cemetery, or spraypainting the side of a cathedral.

In a gastronomic milieu, I'd say the use of mild peppers in a chili would constitute sacrilege, as it would insult the final product and create an abomination that demeans and shames a dish that many approach with reverence. But: To say that Rick Bayless doesn't know how to make chili would be blasphemy.

Quite simply the action of using the peppers is sacrilege.

Talking about using the peppers is blasphemous.

It's that simple.

You can work out which one to use, based on that differential.

(Obviously, the usage is humorous in both cases.)

Thus for example: "that post is blasphemy!" -or- "doing that would be sacrilegious!"