Pretty much wrong across the board.
1) There are MANY people active in the BF community who not only do not assume they exist, but are quite certain they do not. Why those people participate, I don't know, I don't need to be saved from my misguided experiences, but there they are, so ... wrong.
2) You say we'll never know without a specimen. Also wrong. You may not know, but I know. I've seen one, close enough, long enough, that I DO know. I don't have the Liberty Bell but I saw it and I know it exists. It's exactly the same situation. It may not suit your purposes. It suits mine.
3) As above, you might be engaged in speculation. I am not. I saw. I know. Nothing you can say changes that.
4) Could bigfoot exist is not a meaningful question. I have seen. Bigfoot does exist .. whether they can or not. The disbeliever logic is irrelevant to me since existence has been demonstrated to my satisfaction.
5) Their existence is no longer an interesting discussion to me. What I find interesting is figuring out what they are in all the things that can mean.
How's your math ... geometry? You and I are not merely at opposite ends of the same line, we are on skewed lines that do not intersect. We don't agree what the discussion is about. The discussion you are trying to frame is years in my past, I've moved on.
Finally, I do not know with personal certainty that it is in our best interest or theirs to prove their existence. It certainly satisfies our personal curiosity, but at what cost? Many of us struggle with that question and we each have to find our own answer. I'd say the bulk of the people here feel it is worthwhile. I don't have enough information to make my choice. When/if I know enough about them, then I'll know what the cost of sharing is. That's not a choice anyone has any influence on, it's a conversation between me and my conscience.
I hope this makes some sense.
MIB