I totally disagree that engaging in debate with a UKIP member is helpful at all. For starters, they aren't interested in an intellectual debate, it's completely meaningless to them or how they run their campaign. Secondly, giving them a platform helps to legitimise their views with the mainstream, which is why we've had these fringe far right groups able to get footholds in the mainstream all over the world.
Any potential victim narrative they get out of an incident like this is massively overshadowed by the entire country laughing at them, which spreads quickly and works to delegitimise them.