If you are inciting violence or rioting through speech, that can erode society and cause damage that cannot be reversed. Sometimes rioting will improve things, such as in a country that is ran by a dictator, but in freer countries? No good usually comes of it. It's just unneeded chaos.
I think that if the speech itself does not encourage a riot, then it should not be limited by the government since it is a part of the First Amendment. But if the free speech itself is about starting a riot or trouble, then I do not thin there is any problems with the federal government stopping it.
When free speech seems to become obscene or starts to enact violence and rioting, it should not be suppressed, but rather our government should listen closely to the problems that are causing this sort of action by its citizens. Ignoring it or restricting it will only go on to cause more problems.
Regardless of the circumstances I don't believe the Government should have the ability to restrict any of the Amendments at any time, I think the Government needs to address the issues that have angered people to the people where it has reached rioting, limiting peoples rights will only make them even more angry.
The federal government already has laws in place that allow them to restrict the First Amendment when "free speech" reaches a rioting definition. We are allowed to have peaceful protests, not violent ones. We do not need more laws to restrict free speech or more laws to protect violent riots.