You seem to think, and Musk seems to represent, that for most investors, investment is about ensuring each investment, in a vacuum, carries zero risk.
Which is not true. Investors want to know about the risks, in detail, because then they can make informed choices. Maybe they'll adjust how much they invest, or look for offsetting investments (other companies or financial instruments that would go up if Tesla goes down), or do any of dozens of other things. But they can't do that if they don't get accurate information about the company, which is what Musk is supposed to provide.
Being bombastic and arrogant instead of providing accurate information might be good PR in certain circles (like HN), but Musk has, well, literally any other venue he's ever spoken in as a place to be bombastic and arrogant. This is the venue where he's supposed to be actually honest with investors, not the venue to be fake-honest through statements like "not everyone should invest in this" (gee, Elon, that's never been true of any other company in history... oh wait).