Morally I believe we have no choice. Plus think back to your younger days when you have been given good advice - whether you listened or not. :-)

One area where I do keep my mouth shut is the area of stocking up on food. Everyone you try to warn will laugh at you now, but will all be lined up at your front door when they run out. When the greater good for your offspring is to horde food then that is what you have to do.

However, if I see someone who I think maybe hiking to their death then I would have no choice but to stick my nose into their business.