Free speech matters because dissent from the status quo is how the status quo gets changed. If voices which oppose the status quo are consistently denied access to mainstream platforms and are algorithmically suppressed online, they're unable to change the status quo. They don't have free speech in any meaningful sense, because they're actively obstructed from using free speech to do what free speech is supposed to do: challenge existing consensus, norms, systems, and power structures.
Reading by Tim Foley.