Freedom of speech is a cultural value, it's not something strictly defined by the US constitution. It's the reason there is a constitution not the other way around.
There's a lot of incorrect things in this, but to address the incorrect thing most relevant to this discussion:
What you are asking for is called compelled speech. If what you think "free speech" is were true, the government could force newspapers and online news websites to publish articles written by the government that they do not agree with.
I don't understand how anyone reading someone saying something like this doesn't immediately picture some government organization with an authoritarian leader holding the exact same value while considering dissenters a harm to their society.
I agree! KF is expressing their speech just as freely as they did before. But less of society is choosing to support that speech. What do you see wrong with that?
The ACLU also protected racial minorities and queer groups. The "free speech absolutists" who come out in force to protect organizations like KF rarely do that.
So if someone doesn't like what you say (and I presume there are plenty such people), do they have the right to DDoS you too?
Just to be clear this is of course not a threat or anything. I really want to know when you think that speech becomes punishable and who is supposed to decide that.
No, DDoS is a crime. If you support CF dropping KF as a customer because CF doesn't like what KF say, the equivalent argument is that anyone who doesn't like CF has the right to drop CF as DDoS protection.
This is a stupid clichee even on its on terms, but it doesn't even apply here, since shutting down Kiwi Farms does not just impose consequences on speech, it actually directly suppresses speech.