I've never seen anyone say this before. Could you elaborate how? Like speaking over someone so they may not speak?

That's one of the reasons the whole hate speech topic became an issue.

How?

edit: you've just picked another (tautological) form of speech for which you're not explaining how it suppresses the freedom of others to speak. The question-begging word "bullying" here is the hint. The "bully" would refer to it as commentary, not bullying.

Can Donald Trump be bullied? Can a racist mass shooter? "Bullying" is a value judgement.

I think people who kill themselves are pretty much finally suppressed in their freedom of speech.

If everyone is free to speak their minds, how can it be used to silence others?

Even more improbable in the context of cyberbullying. Tyler the Creator's cyberbullying tweet appears to be more relevant than this take.

There aren't many people for whom this would have no effect on the nature and quantity of their comments.

For that, speech is usually more than enough, especially if performed by a large ingroup against a small outgroup.