Stupid users is not good description for people who have either little knowledge or no knowledge on how to use Bitcoin and how it operates. These people usually display their ignorance mainly because they don't understand the whole idea of using bitcoin as method of payment for their transaction of goods and services. Ignorance is usually displayed by People basically due to lack of understanding and knowledge.
Stupid users is somehow a form of a joke term but yeah this was being used by the tech industry. Just like the software development industry usually they let software ignorant people uses their software so that it can be idiot proof.
This may sound harsh but this is also a reality. There are exactly users who acts like they know how does it really works or they feel like just because they have it they fully understood what they have and within this industry we do have a lot of them.