Typically in the US, freedom of speech doesn't face the attacks it does in other regions of the world. However, 2016 especially has seen an uptick in threats to the right guaranteed in the First Amendment. Whenever journalists, filmmakers, peaceful protesters, and others are arrested or their voices somehow muted, freedom of speech is under attack. This is why it's so important to be vigilant of these actions and to fight against them.
Yes, freedom of speech is definitely under attack because it is more and more obvious how people or law enforcements are not allowing people to get together and picket for something they believe in. A few weeks ago, Shailene Woodley got arrested for being at the rally, and many other people got arrested there but they were not doing anything wrong, and their freedom of speech was certainly under attack.
The North Dakota pipeline film makers should not face prosecution: they are merely doing their job and exercising their right of free speech. Vested interests such as the oil industry should not be allowed to put legal obstacle in their path. There is no evidence that the filmmakers are promoting violent protest, they are simply recording it, which is their right.
Yes, freedom of speech is under attack because these filmmakers are simply raising awareness, they were not causing any harm to anyone. Why should they be punished? The country should support people who go out and reveal injustices. Rather than punishing them, we should let the filmmakers inform us of what is happening.