I don't think it's functionally equivalent to suppression of their free speech rights, because I don't believe in free speech as an abstract virtue of society,

I don't think it's functionally equivalent to suppression of their free speech rights, because I don't believe in free speech as an abstract virtue of society, I believe in free speech as a check on the powers of an oppressive government. If you want to tell people about the faults of the government and organize resistance, you're never going to get the support of established media channels, regardless of whether you're in a democracy or a monarchy or a communist state. But it is still important that you be able to set up person-to-person communication networks and hold meetings of like-minded people and try to persuade people to your cause without being imprisoned. I think al-Qaeda's speech acts are difficult to distinguish from a genuine homegrown resistance/revolutionary movement, and I worry that laws that criminalize advocating its ideology can also be used to crush a budding resistance movement and censor the spread of material the government finds embarrassing.