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Google gives Android users a way to install unverified apps if they worked hard for it(including waiting 24 hours)
(android-developers.googleblog.com)
This is a most excellent place for technology news and articles.
The sales rep offered a solution to that person's problem.
You want that person to be right which they perceive as you want to dominate them.
So they try to resist you while they are highly motivated to follow the instructions of the sales person.
Interesting explanation of the psychology and I don't necessarily doubt it, But I also offered a solution. The solution I've offered fixes the problem, the salesman's solution sounds like it solves the problem but does not.
A solution without demand is worthless. At first the demand has to be created. Some people value understanding and are thankful but that's a small minority.