When I came to work at the American Civil Liberties Union, my aunt told me she was proud of me but hoped I would not agree to defend the Nazis. She did not know much about the 90-year history of my organization, but she knew that we had defended the rights of Nazis to march through a predominantly Jewish neighborhood in Illinois in 1978.

Since Barack Obama's election, we have seen a rise in racist expression across the country and here in Maine. I am convinced, though, that unencumbered freedom of expression -- even for ideas that are hateful -- ultimately advances the cause of civil rights.

Reports of racist graffiti on college campuses and racist comments on Web sites discussing our next president have outraged many of us.

Here in Maine, a sign at a general store in Standish solicited bets on when Obama would be assassinated and stated, "Let's hope we have a winner." Black effigies were found hanging from nooses in trees, recalling the lynch mobs that plagued the South from the end of the Civil War well into the 20th century.

These actions have challenged our commitment to freedom of expression, with calls for government censorship and criminal prosecution.

The First Amendment tells us, though, that the government cannot and will not protect us from evil thoughts or malicious speech.

Instead, we are obligated as citizens to criticize racism, sexism, xenophobia, homophobia and any other ideology we wish to discredit. Only by meeting disagreeable speech head-on with more speech can we hope to undermine the power of hatred.

This is easy enough for contentious-yet-civil speech, but the pressure comes -- as it has in recent weeks -- when the speech is unpleasant, distasteful or hateful.

Freedom of expression helped bring us to a day when a black man could be elected president of the United States. The 1963 March on Washington remains the iconic event of the civil rights movement. The Selma-to-Montgomery marches in 1965 drew national attention to police violence and motivated Congress to pass the Voting Rights Act. Marches, rallies, protests and speeches -- all core First Amendment activities -- helped bring us closer to the world we want.

In contrast, government censorship has consistently undermined freedom.

Today, we think of anti-war protests as a fundamental part of public life, but in 1918, socialist leader Eugene V. Debs was sentenced to 10 years in prison for giving a speech critical of President Woodrow Wilson and military recruiting. That same year, groups of immigrants were sent to jail for publishing articles and leaflets critical of American military policy. Others were given significant prison sentences for speaking out against military conscription.

The government has always been a poor arbiter of which ideas should be censored and which permitted to flourish.

Throughout our history, it has been dangerous to oppose war, to criticize the economic order, or to support equal rights regardless of race, gender or religion. But those ideas have been able to gain a following because they have successfully competed in the free marketplace of ideas.

As John Stuart Mill wrote: "The peculiar evil of silencing the expression of an opinion is that it is robbing the human race. ... If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error."

Because I am committed to civil rights and peace activists having the right to freedom of speech, I am willing to go to court on behalf of Nazis and the Klan, so that we all have a chance to see truth collide with error.

The "livelier impression of truth" depends on robust speech and a multiplicity of voices.

That means every individual who was disturbed by the racism directed at Obama is obligated to speak up about it: attend rallies, write letters to the editor, hang signs in your own place of business expressing hope for full racial equality.

It is not the government's job to combat disagreeable speech, it is ours. It is yours. Take it seriously.

Zachary Heiden is legal director of the Maine Civil Liberties Union Foundation, the Maine affiliate of the American Civil Liberties Union, or ACLU.