Maybe the only way is a highly educated population that can't be easily manipulated. However I'm afraid nowadays there are too many channels that facilitate misinformation spreading. At the same time trusted sources of information are not valued, people are less educated on critical thinking and they have a lack of focus capacity that makes them more vulnerable.
Highly educated people are not harder to manipulate than others. There's good evidence that suggests they may be easier to manipulate, even, although personally I think the level of education doesn't affect ease of manipulation, only what manipulative techniques are most effective.
The real problem with misinformation is that some people just want it to be true and so it bypasses all critical thinking checks and then reinforced by post-doc rationalizing, cherry-picking, etc.
Disregarding information you want to believe requires significant effort and discipline.
So the real problem is more around why certain people want to believe certain things. If can address the why, then the misinformation will have no power.
Ask "Are people getting less moral/kind/respectful/honest?". Almost everybody will very confidently reply "yes".
The most correct answer is "I don't know", although there is good evidence for "no".
"Are YOU getting less moral/kind/respectful/honest?"
I wonder if what's going on is more of "progressive alienation with age," where young people basically accept things as they are in their youth, then get slowly alienated by rapid cultural change. Also maybe there's an age discrimination factor as people get older they become less valued/respected by strangers.