I agree that this is a limit on corporations’ free speech. Monopolistic corporations do have a well founded legal limit to their free speech rights.
For example, it’s a form of free speech for Microsoft to decide how they write their own software. One of those decisions was to bundle a free web browser in with their OS and tie the OS function tightly together with that browser. Microsoft Corporation was almost broken up by the government because they did that.
The issue that Greenwald is raising is similarly rooted in anti-trust;
> If one were looking for evidence to demonstrate that these tech behemoths are, in fact, monopolies that engage in anti-competitive behavior in violation of antitrust laws, and will obliterate any attempt to compete with them in the marketplace, it would be difficult to imagine anything more compelling than how they just used their unconstrained power to utterly destroy a rising competitor.
Freedom of speech is not absolute. Just like individuals’ free speech rights have limits such as incitement to violence, corporations also have limits to their “free speech” rights based in anti-trust law and anti-racketeering laws in how they can attack potential competitors.
It's not irrelevant.
> What seems to be under attack here is the right of individual companies and people to decide who they wish to work with.
To the extent that that is based on expressive preference, that is an aspect of free speech, and the closely-related right of free association.
Limiting that right is limiting free speech.