They're not shy in wanting a united Ireland - they even have a song called "get your Brits out" and rap partly in the Irish language, as they claim years of British rule has seen it reach near extinction and they wanted to make it popular again and use it as a means of not wanting to see their culture and heritage die out.
They're very tongue-in-cheek and quite misunderstood though. They actually say they've got nothing against the British people, just those in power, running the country. The British Government refused to give them a lottery grant earmarked for underprivileged artists, because of their background in songs against the British establishment, so the band took the Government to court and won! Their DJ turned up to court in Belfast in an old Police Land Rover used during the Troubles.
You can see why people have labelled them "punk rap".
Also, if you've not seen it, I can recommend Kneecap the film (it's currently on Amazon). It's about their origins and won a BAFTA. It's a really good watch!