On Saturday morning, Ms. Reid devoted about 30 minutes of her show to the controversy, speaking with a supportive panel of experts who fight for L.G.B.T. rights.
“I have not been exempt from being dumb or cruel or hurtful to the very people I want to advocate for,” said Ms. Reid, 49. “I own that. I did it. And for that I am truly, truly sorry.”
Most of Ms. Reid’s guests commended her for recognizing that her words had been hurtful, and redirected the conversation to Washington and the Trump administration’s policies.
“The reality is that while we’re having conversations about what may or may not have been said 10 years ago, we should be having conversations about what was tweeted 10 seconds ago,” said Danielle Moodie-Mills, a public relations executive who hosts “Woke AF” on SiriusXM, the satellite radio provider.
“There are bans that are still up at the Supreme Court right now to keep Muslims out of America,” she added, as well as efforts to “kick patriotic trans people out of the military. And that’s coming from the Oval Office right now.”
Ms. Reid’s posts emerged on social media this month via the Twitter user @Jamie_Maz. In December, the same account shared posts in which Ms. Reid taunted Charlie Crist, the Democratic former Florida governor, as a closeted gay man whose heterosexual marriage was a political front. Late last year, she apologized and Mr. Crist responded, “Long forgotten, but thank you, Joy. I appreciate you.”
It’s not the first time Ms. Reid’s words have stoked controversy.
On Saturday she apologized for some of her past tweets, including ones in which she mocked the conservative commentator Ann Coulter by “using transgender stereotypes.” Ms. Reid grew up in a household that had conservative values on L.G.B.T. issues, she said, but “those tweets were wrong and horrible.”
“I look back today at some of the ways I’ve talked casually about people and gender identity and sexual orientation and I wonder who that even was,” she added. “But the reality is that like a lot of people in this country, that person was me.”
She did not take ownership of the most recently surfaced blog posts, however. In a statement this week to Mediaite, Ms. Reid said that her website had been breached and that the posts were fabricated by hackers intending to defame her.
She said in the statement that “an unknown, external party accessed and manipulated material from my now-defunct blog,” and that she had retained an online security expert to investigate. “I can state unequivocally,” she wrote, that the resurfaced posts do “not represent the original entries.”
Ms. Reid’s former blog posts were discovered via the Wayback Machine, an archive of more than two decades of web history. On Tuesday, the Internet Archive, which runs the Wayback Machine, responded to Ms. Reid’s claim that her posts had been hacked, saying in a statement that it had found no evidence of hacking in the archived versions of her site.
Ms. Reid’s security consultant, Jonathan Nichols, responded that “at no time has Ms. Reid claimed that the Wayback Machine was hacked” with an intention to alter her blog. Instead, he said Ms. Reid’s team detected a “breach” of her blog but that it was unrelated to the “fraudulent” posts.
Ms. Reid ran her blog, “The Reid Report,” in the mid-2000s while writing about politics for The Miami Herald, long before she started working at MSNBC, where she once had a daily show with the same name.
She has emerged as a rising star at MSNBC, galvanizing liberal viewers with her forceful interviews with supporters of President Trump and tough commentary on politics and race. “AM Joy,” her morning show, has risen in the ratings since its debut in 2016, and Ms. Reid was a frequent substitute for the network’s marquee prime time hosts, including Ms. Maddow.
Ms. Reid is also a columnist for The Daily Beast, whose executive editor said it “hit pause” on her columns while it investigated her claims that she had been hacked, CNN reported.
The Daily Beast said it found errors in Mr. Nichols’s methodology and concluded that “the indicators of hacked posts don’t bear out.”
On Saturday, Ms. Reid noted that she “should have known better” than to have ever written or tweeted words that were homophobic or transphobic, “even a decade ago, when the country was in a very different place.”
“But I cannot take any of that back,” she added. “I can only say that the person I am now is not the person I was then.”