First, I want to say that freedom of speech is a moral issue, not a political one. The US Constitution is a vital document, and the First Amendment is very clear about what the government can and cannot do when we say something people don’t like.
The U.S. Constitution is a flawed historical document at best. The fact that many in the U.S. continue to embrace its vitality doesn’t make it relevant or just in contemporary society as a whole. Furthermore, as the Internet is a global platform that transcends local and national laws, it is better that we look to international standards for evaluation frameworks.
To your point about morality, for example, the U.S. has never been a harbinger of justice nor a role model for global morality. Quite the opposite, people look to the U.S. when they need an excuse for bad behavior. It’s ok to be unethical in America. The Constitution says so.
As such, relying on Constitutional morality severely undermines your argument. It’s an important argument, though, so I strongly recommend researching beyond our own borders for moral and ethical standards with global applicability.