Baltimore Ravens linebacker Brendon Ayanbadejo has been a consistent supporter of legalizing same-sex marriage. In 2011, he filmed his own video backing this November’s ballot initiative in Maryland and posted it on YouTube, and he recently donated Ravens tickets to a Marylanders for Marriage Equality fund-raiser.

Ayanbadejo’s acts caught the attention of Emmett C. Burns Jr., a Maryland state delegate who opposes same-sex marriage. On Aug. 29, Burns sent a letter to Steve Bisciotti, the Ravens’ owner, urging him to “inhibit such expressions from your employee and that he be ordered to cease and desist such injurious actions.”

Burns’s letter elicited an aggressive, searing response from another N.F.L. player, Minnesota Vikings punter Chris Kluwe, who said he could not sleep after reading the letter Thursday night because he was too infuriated. So he wrote a profanity-laced response to Burns and submitted it to Deadspin.com.

“Your vitriolic hatred and bigotry make me ashamed and disgusted to think that you are in any way responsible for shaping policy at any level,” Kluwe wrote, adding later: “Why do you hate the fact that other people want a chance to live their lives and be happy, even though they may believe in something different than you, or act different than you? How does gay marriage, in any way, shape or form, affect your life?”

Kluwe’s letter, which has been lauded by many supporters of same-sex marriage since it was posted Friday, has offered a change in perception. The N.F.L. has long fought the stigma of having a homophobic culture. Now, two pro football players have powerfully lent their support for same-sex marriage, taking a political figure to task in the process.

“It was unexpected to a lot of gay people to have someone from the most masculine sports league in the country come to the defense of the gay community and attack this person,” said Cyd Zeigler, a founder ofOutsports.com. “It was unexpected, and it was awesome. To see the clear passion for this topic, I think, was energizing.”

The support offered by Kluwe and Ayanbadejo is timely, because Minnesota and Maryland are among four states that will have same-sex marriage votes this November. In Maryland, Maine and Washington, the legalization of same-sex marriage will be on the ballot. In Minnesota, there will be a vote on an antigay marriage constitutional amendment that, if passed, would define marriage as a union between a man and a woman.

“These guys are heroes,” Brian Ellner, a leading marriage equality advocate, said of Kluwe and Ayanbadejo. “This kind of thing has never happened before. It matters because Brendon and Chris are professional athletes who are uniquely positioned to help shape opinions and say to fans, to people who may not be focused on this, that gays are just like you and me.”

In the past week, Ayanbadejo has been contacted by supporters in Brazil, Norway, England, Australia, Colombia and Ireland. He has also been overwhelmed by the support of his Ravens teammates and other N.F.L. players. “I’d say the majority of players are siding with me, that all people have a right to live and love and be happy,” Ayanbadejo said in a telephone interview. “That’s really amazing. I’m very happy to see the tides changing in the positive.”

Kluwe, whose brother-in-law is gay, said all but “four or five of about 6,000” messages he had received on Twitter in response to his letter were positive.

“I think the culture in the N.F.L. has become a lot more tolerant in the last 10 years or so,” Kluwe said in a telephone interview. “There’s a younger generation coming in every year or two, and they make me hopeful of the future.”

There has never been an openly gay active N.F.L. player. In 1975, the former 49ers and Redskins running back David Kopay said he was gay. Roy Simmons, a former guard for the Giants and the Redskins, came out in 1992, and the former defensive tackle Esera Tuaolo, who played for five teams over nine seasons, did so in 2002.

And, Ellner said, support for gay-rights issues is on the rise in the league. The current and former N.F.L. players Scott Fujita, Michael Strahan and Nic Harris are among those who have spoken out in support of same-sex marriage. The Hall of Fame wide receiver Michael Irvin, who had a brother who was gay, appeared on the cover of Out magazine. Zeigler said he had interviewed 25 current players in the past year, all of whom said they would welcome a gay teammate.

Perhaps most noteworthy, in August the San Francisco 49ers became the first N.F.L. team to join the It Gets Better campaign, creating an anti-bullying video in support of gay, lesbian and transgender youth.

“I think it’s a transformational moment and seismic shift to see so many folks in the world of sports stepping up and speaking out in support of equality and fairness and, in this instance, marriage equality,” Ellner said. “It really demonstrates what we know, and what’s apparent in the polls, and that the world has changed.”