I think the reason so many people feel that it's important to allow dissenting and objectionable speech is that the perception of 'harmful' speech is mostly subjective.
Relegating that permissiveness to a particular entity allows that subjectivity to be enforced in perverse ways.
Many people feel it is better to tolerate the objectionable and hurtful speech than to allow a 3rd party to use subjective judgment to censor.
It's not implemented well enough to detect the fine differences between western countries.
Hate speech laws reduce the range of discourse. They suppress dissent. That's inherently undemocratic.