You had me until you veered off into the woods with talking about actual desecration of physical items that may or may not belong to you*. A more apt but-still-not-quite-accurate comparison to this topic would be some people trying to change the genders of the characters in religious text (which I guess would still be desecration to some people, but that's getting into an argument about semantics).

*I would consider myself an agnostic at best, but to attempt to answer your question, how I'd feel depends on who the item belongs to. If someone goes and destroys an actual historic item, like preserved text or a statue, I'd be angry simply because they're vandalizing something that doesn't belong to them, regardless of my religious belief. If they're destroying their own personal property, that's on them, and I'm a pragmatic man so I think I'd feel the same way even if I adhered to a religion that held that particular item to be sacred.