I wonder if the last point is not so much hostility but black-hat brainstorming of what could go wrong, particularly if your counterparty believes they have some experience that you don’t have.

If someone comes to me with an idea for an idea of how to solve a problem in a space I know well and (as far as I know) they don’t know as well, my comments are likely to be at least 2:1 negative:positive. It doesn’t do them any good for me to tell them how awesome it would be for their idea to revolutionize the world. They already feel that. They more likely need to here where they’re likely to struggle or refine/test their idea before sinking thousands of hours into it.

Maybe that’s a possible underlying (positively motivated) driver for the negativity you experience?