For anyone that has never had a conversation like this, you really have to be careful with this and pick your battles wisely. Some people are so non-technical, that they will not understand what you are explaining to them, or why you are even bothering them. You will be perceived as a tinfoil hat wearing conspiracy theorist. Some people will understand what you are explaining and might even understand your stance, but ultimately will still continue in their ways because it's so much easier and convenient.
What ever you do, don't be judgemental about their decision. You will only make them less interested. Start slowly. It can be overwhelming how fubar'd the web experience has become.