Castro, 44, had asked Biden, 76, on Thursday night whether he forgot what he said on health care just "two minutes" before their exchange. For "The View," that comment seemed like a clear attack on Biden's age -- an issue that's been raised multiple times during the 2020 primary season.
"This 'old' thing has got to stop because 25 percent of the electorate is over 65, and they vote. I'm one of them," co-host Joy Behar said.
"And I vote, so be careful what you do with old people because we will turn on you," she added. Behar went on to question Castro's own mental abilities, arguing that he seemed not to learn a lesson from Sen. Kamala Harris, D-Calif., whose poll numbers rose but then dropped shortly after attacking Biden at the first debate.
Co-host Abby Huntsman suggested that Castro's attack was likely the last "nail in the coffin" of the former HUD Secretary's 2020 bid.
Co-host Whoopi Goldberg flat out told Castro, "Don't do that," while Sunny Hostin, another co-host, said Castro's attack was "stupid."
"I think it was just such poor form on Julian Castro's and it's stupid," she said, before listing the ages of President Trump, Sen. Bernie Sanders, I-Vt., and Sen. Elizabeth Warren, D-Mass. "Joe Biden is one of the younger ones. He's 76, and Trump is older as well so it was very, very tone deaf."
"My first tweet of the night was, 'Oh, I forgot Julian Castro was running,' because I legitimately -- that's how dumb his campaign has been. So, he was clearly looking for a cheap shot, attention which, congratulations, you did for one moment on 'The View.'"
"Put a fork in it, the campaign's over," she added before describing Castro's attack as a "Trump tactic."
When she addressed Booker's comments, McCain also knocked the senator's low poll numbers. "He said, 'there are a lot of people concerned about Joe Biden's ability to carry the ball all the way across to the end line without fumbling,'" she said, recounting Booker's comments to CNN.
"Well, you don't even have the ball at all, Booker. Like, you haven't even caught it so maybe you should give Joe Biden a break for the fact that he has the ball and he's carrying it and doing well."