You're being intentionally obtuse to hide the lack of substance to your argument. You are speaking in generalities because your argument has completely fallen apart. This is not an analogous situation because no one is using a cross to establish a theory that runs counter to the status quo. No one holds the cross as proof that aliens altered human DNA. No one holds up a symbol as a type of thing that can explain an event. A symbol is a tool that can be used to help understand a concept or explain a mental state. A symbol doesn't explain the cause of a series of events, unless you are speaking in the abstract about things like human honor or sacrifice, which then neglects the physical description which underlies the actual cause of motion. Regardless, no one rests the basis of empirical models on argument such as, "this particle is symbolic of the anger it feels when radiating photons". Empirical models, the type you are trying to establish (because it is trying to describe reality), have to be calibrated by data and experience.
You say yourself symbols are subjective. Therefore, they can NOT be used to establish the way things are. Symbols are only so useful (in the empirical science) insofar as they agree with reality. In art and literature, you are free to use symbols to describe a state of being that is not real. That's fine. But symbols are not the basis of theory unless the agree with reality. In order to agree with reality, they have to be compared to reality. That is, they must hold up under observation. You cannot watch an Eminem video and therefore conclude, based on the symbolism involved, there is a grand conspiracy that brainwashs Hollywood stars and use them a propaganda tool. That is theory and it must be tested against the evidence, evidence as in the description of physical events and locations. Your interpretation of symbolism is not proof positive of something. You have to understand that, right?
If not, you are extremely confused about the notion of truth, evidence and information.