One of my favorite all time quotes, from Barney Rubble - "well, Fred, you can lead a horse to water, but you can't make him read the book".
Kind of think of this as the plight of the typical parent trying to share some experience with their young children in hopes that they can help their child learn the lesson without having to learn the experience first hand. From one child and situation to the next, sometimes children listen to what they are told, others, they have to learn the hard way by their own first hand experiences and mistakes in order to say "gee, mom and dad were right"; this I know as I was one who in my younger years was not good at learning from others advice, I had to learn my own way, first hand, by making the same mistakes others tried to shield me from with their advice.
This is also like the old quote - you can catch more flies with honey than vinegar. In this case, being blunt and honest with people, especially those close to you and loved ones, about some of the world's harsh realities that a lot of people insist on seeing and treating as theories, is the vinegar in this case. With a lot of people, too much brutal honesty too soon merely sends them furthter into denial. Planting seeds is the honey. Rather than taking the direct and blunt honesty route, planting seeds involves a subtler approach, like casually observing or pointing out harsh realities only as real-life circumstances occur. Sitting around at family functions, especially spring and summer time get togethers, picnics, etc., whentopics are likely to spring up among conversations, is a good time for conversation to occur on real-life realities (government, health, economy, history, wars, etc) , and thus a good time for planting seeds. Give them enough to, you hope, eventually chew on, dwell on, think about, on their own at their own pace. Then hope that the world does not blow up in the mean time that it takes for them to contemplate on their own well enough that the light bulb finally come on in their mind.
Lastly, when it comes right down to it, one can only do so much on behalf of others. Difficult as it may be, at some point you have to leave people, even loved ones, to their own devices. At this point, when all hope for them seems lost, you can always resort to prayer.