A lack of knowledge about how the world really works can lead to the end of civilization. This is true because knowledge serves as the building blocks of life, and putting those blocks in the right place and order can create a better future. Those building blocks can create bridges to the past; linking important events to create an understanding present realities.
People who lack knowledge can become quite dangerous under certain circumstances. The most dangerous are those who would use force for unjust and selfish causes. While what is considered unjust and selfish is subjective, there is no doubt when and if harm occurs. Unthinking passions can quickly transform peaceful situations a free-for-all absent of reason and full of anxiety.
Ignorance is bliss, as the cliché often goes. In some cases it is not dangerous, at least for those with no proclivity to do harm. However, for those who wish to do harm, or simply do not care, they represent a clear and present danger to those around them. The worst part is that those who commit harm will be unaware of the effect their actions have, thus showing a lack of humanity.
An ignorant individual is dangerous when augmented by others: falling prey to the herd mentality that is the secret weapon of a tyrant. Becoming ensconced with others and their destructive thought processes provides a false feeling of safety and security. People comport themselves as an army of lobotomized sycophants with no original thoughts in their head. By this point they are hanging on every word of the demagogue, ready to destroy civilization.