Copyright claims are often used as a way to keep people from being able to talk about important issues. There are other legal maneuvers sometimes used to stifle free speech. Fortunately, some states have strong Anti-SLAPP laws!
In case you're new to the subject, SLAPP stands for a Strategic Lawsuit Against Public Participation. In short, SLAPP suits are lawsuits where it is fairly obvious that the intent of the lawsuits is to stifle free speech, rather than for a legitimate purpose under the law. The intention of anti-SLAPP laws are to allow for such lawsuits to be tossed out of court quickly -- and, frequently, to force those who bring those suits to pay legal fees.