Why I'm Not A "Unionist"
One of the main techniques extremist groups like Nationalists use to make themselves appear normal is to label their opponents something they would like them to be and then attack that label.
By labelling their opponents as “Unionists” or “Yoons” they associate them with Union Jacks, British bulldogs, Churchill, and The Queen.
(Of course the Union that the Nationalists almost always imagine is English — they never include Northern Ireland or Wales, or the Scottish people who are part of Britain.)