We can't honestly, with any integrity, call it proof until mainstream science accepts existence of bigfoot. That is what PROOF means. There is no real proof but scientific proof, any lesser proof is not proof, "proof" is the wrong word for that whether it is used from ignorance, illiteracy, or just stubborn malice. There is no way around this.
You seem to not understand what "proof" means. You're trying to change the definition / refusing to use the existing definition. Best of luck convincing anyone but yourself with that.