Cancel culture is Alice's fighting Bob by demanding Charlie stops doing business with Bob.
In its most extreme form, Alice can kill Bob with it by demanding Charlie stops selling or providing essential goods and services to Bob such as food, water, or healthcare, or the employment needed to get the money to purchase the goods and services.
So the unrealistic worst-case scenario of this quasi-banishment is extrajudicial murder. A more realistic worst-case scenario is the creation of parallel societies where the Alices and Bobs live their lives and run their economies separately from one another since they cannot coexist.
Even then, one of the parallel societies is likely to suffer more since modern society has come to depend on privately-owned infrastructure that are difficult to replace or compete against. Even a simple Internet forum depends on a large list of privately-owned infrastructure, ranging from telecom infrastructure to financial institutes, and still must fight against the network effect in order to be successful or solvent.
Another reason one of the parallel societies is likely to suffer more is because natural resources do not care for where the borders of each society go. Thus it's quite possible for a parallel society to be left without access to a natural resource that is essential for a modern society.
Is this really the path we want society to go? Is it really reasonable for Charlie to stop doing business with Bob because Alice demands it?
It's not like Charlie really cares about what Bob is doing. Plenty of Charlies do immoral shit in Timmy's backyard such as child labor, sweatshops, polluting the environment, or doing business with Timmy while Timmy commits genocide, yet Bob's saying stupid shit is where they supposedly draw the line?
We took away the power of monarchs and government to banish people for a reason. So why stop there? Why not take away society's power to quasi-banish people as well?
Not wishing to hang out with undesirable people, refusing to buy goods or services from them, refusing to use their services, or refusing to work for them, is one thing.
Denying them goods, services, or employment, is another thing entirely.[1]
[1] For those bringing up the gay wedding cake: if it's not a standard product they're selling, then I see it as a commission. In other words, they're not denying you goods or service. You're the employer and they're refusing to work for you (much like, say, a DeviantArts artist's refusing to draw porn commissions).