If you were to say, make a pro-ISIS video, or Tweet, would you expect to remain unmolested by the authorities in the United States? All societies set boundaries on what is acceptable speech.
I would expect making a pro-ISIS video/tweet to leave me without additional molestation from the government, yes. Probably wouldn't stay up on YouTube, but other sites don't seem to have a problem with such things. (stereotypically, that would be LiveLeak)
You can check out the list of exceptions to free speech in the US here [0]. I disagree with a number of them, but an "ISIS is awesome and this is why" video would fall under none of them. (the same goes for a "Hitler was awesome" video, a "Trump is awesome" video, or a "Trump is a fascist and we need to rise up in violent rebellion" video)