Is doublespeak built into English?

I’m thinking about the word believe.
Believe (transitive verb) according to the Merriam-Webster Dictionary means:
1. a. to consider to be true or honest.
1. b. to accept the word or evidence of.2. to hold as an opinion: SUPPOSE
Merriam-Webster is on the conservative side with the definition of the word. Dictionary.com is more inclusive of its daily use and the range of its coverage:
2. to have confidence or faith in the truth of (a story, etc)
all the way to
6. to suppose or assume, understand.
The word is stretched quite thin on the spectrum of having absolute confidence and making a casual assumption.
Let me put it in context. Consider a person who says:
“I believe Neo will save the world.”
Meaning that he has a strong conviction that Neo will save the world.
vs.
“I believe Elvis has left the building.”
In which case he merely guesses the whereabouts of Elvis.
Now how can we trust the convictions of this person? His first statement could drive his followers to also believe in Neo. If Neo fails, he can simply claim that he never actually trusted that Neo will save the world. That he was just guessing. He would technically not be lying, he would be using the language correctly. It’s the language itself that would have allowed his doublespeak.
This, I find problematic. A glitch in the language itself, leaving lots of room for interpretation of its use. But more importantly, it wires brains, the brain of a child, the collective brain of a society in a particular way. It is too flexible. It seems to lack integrity.
Another example where “believe” is used as an intransitive verb:
“I don’t believe in climate change.”
vs.
“I don’t believe in miracles.”
In this case, the verb “believe” allows for any object that follows it to hold equal weight and value. Any given fact or lie, scientific evidence, or superstition alike fall into the same pool of objects that can be believed in. It all comes down to how the subject can exercise “belief” on a wide spectrum of firm trust and light assumption.
I don’t feel comfortable with the word “believe”s range of coverage in English. Perhaps this has to do with how it translates in my mother tongue, Turkish, plus religion and spirituality’s dominance in the culture, and my own upbringing. In Turkish, the word translates to inanmak (v), inanç (n). It describes a firm trust. If you believe in something you trust in its truth from the heart. This does not compromise the internal consistency of the believer nor the object of belief. Ultimately, whether you believe in them or not, facts, truth, God, or miracles exist independently of you, unaffected by your position about them. In the English language, all that becomes diluted along with the flexibility of the word “believe.”
Much of the latest political mayhem taking place in the US, the words that come out of politicians’ mouth pulled in so many directions, leave the public in a limbo of ultimately believing whatever they want to believe in, and the traditional media which is supposed to have some power over public opinion utterly helpless at steering it towards the truth.
I wonder, is it at all possible to anchor meanings back into words, and restore trust by continuing to use verbal language? Or will we have to discard language itself as a central tool to uphold trust and constitution in societies?
Note: This is a quick sketch of my thinking for an art project which may lead to deeper research. I’m interested in powerful words in English, or in any other language which can stretch out in meaning, and have an impact on the way societies think and behave. I would much appreciate it if you commented and pointed me towards good resources.