Revelers celebrate during the Gay Pride parade on June 26, 2011 in New York City. (Photo by Mario Tama/Getty Images)

Our founding fathers created a nation built on the power of its citizens and drafted the U.S. Constitution to guard against tyranny by any singular or majority power.

As Americans, it is up to each and every one of us to fight injustice and inequality when we are faced with it. Today, we are faced with such injustice in the form of discrimination against same-sex couples, who deserve the same freedom to marry as anyone else.

We cannot be part-time advocates for justice. When we fail to stand up to tyranny, we leave an opening for an attack on our own civil rights. The issue is not about being gay or straight but about the civil rights of Americans who are seeking to have the same rights and protections as their brothers and sisters across this great nation.

We can’t stand on the sidelines

Certainly, having the same rights and protections must apply to marriage: the cornerstone of our families, our neighborhoods, and society at large. We cannot stand on the sidelines as loving and committed gay and lesbians are denied the freedom to marry. Our fellow LGBT citizens are faced with discrimination in their jobs, their communities, and their everyday lives. Because of the federal Defense of Marriage Act (DOMA) and state laws like California’s discriminatory Proposition 8 legislation banning same-sex marriage, gay and lesbian couples are treated as second-class citizens.

That’s why the American people are demanding change. According to a recent Washington Post-ABC News poll, a bipartisan majority of Americans — 58 percent – already support the freedom to marry. That number leaps to 81 percent among voters under 30.

The African-American community has played an important role in our country’s evolution on this issue. Our president, as well as our religious, civil rights, and community leaders have increasingly recognized the similarity in our struggles – and the importance of standing together in the face of oppression. A majority of African-Americans now support the freedom to marry for same-sex couples and recognize that equal rights for gay and lesbian couples change nothing in our marriages, our churches, or our faith.

Gay marriage is not a threat to religious freedom

One of the key questions before the Supreme Court this week is whether the freedom to marry infringes on religious freedom. As a Baptist minister, religious freedom is something that I believe in deeply and feel is intrinsically woven into the fabric of our nation. But just as I believe that religious freedom allows me the freedom to preach and believe as I choose, it also means that I do not have the right to impose my beliefs on anyone else. It should not be within anyone’s power to tell a religious institution that they cannot marry a loving, committed same-sex couple in their faith.

I am urging the Supreme Court to end DOMA and to extend the freedom to marry to all couples: gay or straight. It’s the right thing to do, and it is crucial for our nation to affirm that we are a nation that values freedom and the equal treatment of all our citizens under the law.

Rev. Al Sharpton is president of the National Action Network and the host of MSNBC’s “Politics Nation.” Follow him on Twitter at @TheRevAl.