It turns out that Eric Harris, one of the killers, maintained a web page drenched in hate. Harris reportedly shared information on how to make bombs over the Internet. Rights can be abused, but the alternative to a free society is one in which Big Brother gets to decide what speech is acceptable and what is not. Of course, the right of speech hardly implies that law enforcers cannot follow publicized comments and use such comments in their investigations. The threatened student shared this information with the police.
Parents also retain rights to monitor their children's behavior.
Harris's parents were fully capable of monitoring their son's activities, and his public documents, and taking preventative action. Apparently, they failed to do so. The Federal government could control the Internet, but it ought not. We must protect evil speech from the control of the government so that the beautiful, the enlightened, the unusual, and the genius can also thrive. Movies and music have also been targeted by some.