CHILMARK, Mass. — This is what McCarthyism evidently looks like on Martha’s Vineyard.

Alan Dershowitz is holding court on the front porch of the Chilmark General Store, talking to old friends and complete strangers, nearly all of whom stop to tell him, between sips of their iced coffee, to keep doing what he’s doing. A young girl compliments his T-shirt (“Kids and Guns Don’t Mix”). His cellphone buzzes constantly, mostly with calls from reporters. “Inside Edition,” the tabloid-style newsmagazine show, wants an interview. So does The New Yorker.

I did, too. I had called Mr. Dershowitz on Tuesday to tell him I was going to be on the island for a long-planned vacation, and I suggested we get together to talk about the stir he kicked up when he wrote, in a column for The Hill, that he had been subject to McCarthy-like shunning tactics from people in his Vineyard social circles. For some of them, his aggressive questioning of the legitimacy of the special counsel investigation into President Trump was indefensible and unforgivable.

He said I should come over to his house. I said I’d rather meet somewhere more public. I wanted to see firsthand how the Harvard University law professor emeritus who helped acquit O.J. Simpson of murder charges — with minimal apparent damage to his social or professional reputation — was handling the backlash to what some believe is his gravest offense: defending Mr. Trump.

“I’m enjoying this,” he told me. “It’s a red badge of courage.”

He said he believes political debate today has essentially degenerated into a fight over one question: Are you for or against Mr. Trump? “We live in a Red Sox/Yankees world,” he said. “And you have to pick a team.”