People can only take in what their minds are ready to hear. One things I try to do is make things into "I" statement. So instead of saying "artificial sweeteners are dangerous and no one should be eating them" I would say something like "I found that when I removed artificial sweeteners from my diet my appetite decreased or my craving for sweets decreased or my intestinal issues went away". I guess that's a gentle nudge rather than a persistent nag. Mostly I don't believe I'm very successful in convincing anyone of anything but maybe, just maybe, I help plant the seeds of better health in some people. These seeds will sprout in their own time.