Liberal Forum

This is actually quite common, but denied by conspiratorial liberals.  One of the companies that facilitates hiring of paid protesters is called Crowds on Demand.  They are one of the companies that is more brazen.  From their website:

Crowds on Demand is your home for impactful advocacy campaigns, demonstrations, PR stunts, crowds for hire and corporate events. Services available nationwide.

We are best known for organizing passionate demonstrations, rallies, flash-mobs, corporate PR events, and light-hearted events such as paparazzi, brand ambassadors, and PR stunts.

https://crowdsondemand.com/