I can completely sympathize with not wanting to torture yourself with Harry's insufferably smug voice.
The accusation against IH is mercifully a relatively short part of the video, just under half an hour. To cut a long story short, the accusation of plagiarism is actually valid, as IH copied both the format (the hour by hour structure) and several passages from the article, with the words changed a bit, originally without crediting it in the video or the description. The website where the article was published filed a copyright claim and the video got taken down, and it got put back up a few months later with more words changed and with sources, including the article, credited in the video and description.
It's very much a hit piece, though, even if the accusation is valid. Harry deliberately makes out IH to be a right-wing extremist to rile up his own SJW followers, and portrays IH as deliberately trying to cover up his plagiarism (because he didn't specify why the video got copystriked), when it actuality it looks like he and the publisher of the article came to an agreement behind the scenes without the need for drama.
Tommy Tallarico has nothing to do with IH, he's the subject of Harry's previous video. It's just his fans being unfunny retards.