The statement is somewhat misleading and can be considered false in the context of how free speech is generally understood. While private companies, including social media platforms, do have the right to establish their own terms of service and community guidelines, which may limit certain types of speech (such as hate speech, harassment, or misinformation), this is not a violation of free speech in the legal sense.
In the United States, the First Amendment protects individuals from government censorship, but it does not prevent private companies from moderating content on their platforms. As such, social media companies can enforce rules that may restrict certain expressions, as they have their own policies regarding acceptable use of their services.
So, while they can limit what users say on their platforms, that does not equate to violating free speech rights as protected against government action.