What are situations where a particular group is thought to be a danger or menace to society?

The answer is Moral Panic

Also called 'Public Fear', it is described as a collective Public anxiety or a feeling of threat towards a particular situation which they believe can completely destroy the society they live in.

In history, there has been several cases of Moral Panic starting from early times when e.g. the Japanese saw foreigners as a threat or when so-called witches were burned in Europe.

Recent moral panic examples include the threat of Communism, HIV as a 'gay' disease and the threat of Global warming.

In history, many governments have created 'Moral Panic' as a propaganda tool in wars and to deviate public perception.