Not watching a video, but I take it this is a defamation suit? If so, he doesn't have a shot in hell.
Brendan's a public figure, and he became one by his own doing. It's extremely difficult for public figures to win defamation suits. If it wasn't, every celebrity and politician would be filing dozens of defamation suits every day, and every parody show like South Park, Family Guy, or that pile of steaming trash known as SNL wouldn't exist. This is why Kyle Rittenhouse isn't going to be successful suing anyone who said anything about him after the interview he did with the Washington Post in January of 2021. The only reason why Nicholas Sandmann was able to take CNN to the point of settlement was because he was a private citizen who the network attacked unprovoked by showing a selected snippet of a video that portrayed him negatively without showing the part of the Native American guy approaching him first. For a public figure to prove defamation, they have to demonstrably show a negative impact on their lives as a result of something wholly unsubstantiated that someone said about them either out of malice or indifference.
But hey, if Brendan wants to pay a lawyer and ultimately have to foot the bill for this Youtuber's legal fees with nothing in return, then he should go for it.