"Let the buyer beware" and, conversely "Let the seller beware" describe cultural attitudes regarding persuasion in commerce. Governments at the federal, state, and local levels attempt to protect the public from those who profit through exploitative advertising.
Medical products are tightly regulated because of their potential danger to those who might unwisely purchase medications they are not sufficiently informed to self-prescribe. Cosmetics, on the other hand, can be sold with the wildest claims of benefits. (although the ingredients are still highly regulated)
What we put in, or on, our bodies on a daily basis is very important. We institute authorities who watch over us, lest we unknowingly use something that is dangerous to our well-being.
But what about ideas and beliefs? It appears that these are not nearly so important. We each are our own authorities about the merits of this or that belief system. Currently, Truth is of so little consequence that you can have your truth and I can have mine.
My Teacher disagrees. "It is impossible that destructive persuasions do not come. But let the one be fully warned who convinces vulnerable people to bring harm to themselves. It would be better for him to be thrown into the sea with an anchor tied to his neck than for him to convince a vulnerable person to bring harm to himself. So, beware!"
What about my opinions which I freely hand out over coffee or a meal? Am I aware of what is really at stake if someone takes into their mind and heart what I'm "selling?" What about you? What are you promoting regarding how people treat each other? How freely do you give advice? And what kind of warranty do you provide for your unwise counsel?
What might be different about our world if we all treated other's minds and hearts as sacred? What if we protected our innocent little ones with a little more time to develop keen and informed consciences? What if we took to heart the most important matters of faith, mercy, and justice in view of an eternal day where there will be a reckoning for our counsels?
"You have neglected the more important matters God requires-- justice, mercy and faithfulness." Jesus