The song is “Someone’s Gonna Die” by Blitz, from 1981, if it doesn’t already say that.
There is a great article by the music journalist Garry Bushell, who was, along with others, at the center of the Oi! scene in the UK in the early 80s. But its terrific detail does beg the question, if it’s so hard to explain a genre, perhaps people who have a problem with it can’t be all wrong.
In the excellent Don Letts documentary “The Story Of Skinhead” an interesting point came up when they started talking about Oi! You could like the music, but you had to be white to go to the shows. The first wave of Oi! may have been all leftist, but it was inclusive enough to tolerate the far-right, and that very call for unity, I think, when it was naive, led to a second wave, Rock Against Communism. Bands like Skrewdriver. The kind of stuff that, if someone offered you a chance to listen to a Skrewdriver cassette back in the 80s, it was a sign that you couldn’t hang out with them. Or … I guess that’s up to the individual. But that’s the kind of thought process Oi! does lead to, after all.