Here's why:
* Negative connotations: A collective noun for rioters would likely have strong negative connotations, making it undesirable.
* Variety of motivations: Riots can be sparked by a wide range of factors and involve diverse groups, making it difficult to find a single term that captures the specific intent of the crowd.
* Focus on action, not the group: The emphasis in describing a riot is usually on the act of rioting itself, rather than the collective noun for the participants.
Instead of a collective noun, you might use descriptive phrases like:
* An angry mob
* A rioting crowd
* A throng of protesters turned violent
* A group of people on the verge of unrest
Ultimately, the best way to describe a group of people about to riot depends on the specific context and the desired tone.