Dissident groups challenge the authenticity of government. They break laws and cause riots. Think of the dissident groups of the 1960s that fought for Civil Rights and against the Vietnam War.
Absolutely, government should not only tolerate but heed the messages of dissident groups!
Read the words of two of our earliest dissidents.
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Government does not easily tolerate it in my experience. What is allowed is only the result of fear on the governments part of what courts or the public will do in response. This is why many times the governments response is secret...thru the FBI, or police, or IRS, or social security administration, or else.
What is effective is a healthy press, independent, with backbone, and with courts that are not afraid to air dirty laundry, even in the face of retribution by the executive branch.
President Nixon set the mark for secrecy and criminal acts, and he was only stopped by independent agencies who demonstrated courage. There have been instances since then.
Evil lurks within the hearts of powerful men, and it is incumbent on citizens to stand against them. Often, these folks are called names, dissident being one of the nicer terms.
If you stop to think about it... the colonists were dissidents, protesting the unfair laws that England was imposing. Women's right to vote was not enacted until the 20th Century...and then only because women were "dissidents". The Civil Rights act was only enacted after dissidents made themselves impossible for the government to ignore. People who are willing to stand up and yell verrrrrry loudly....that is not right! are essential to progress in a democracy or for that matter in any government.
It often depends on what's at stake. Dissident voices are a lot easier to tolerate in times of peace than times of war. Also a secure government will tolerate dissent far more comfortably than will an insecure government.