If the federal Liberal brains trust wants a compelling reason why it should rule out a preference deal with One Nation and return to putting Pauline Hanson last, it should look no further than the final week of the Western Australian election campaign. Not merely did Hanson’s noxious views on vaccination and Vladimir Putin suck the oxygen out of the rest of the campaign, the context was always that this was a person the WA Liberals were preferencing ahead of Labor, the party that, in the words of a senior cabinet minister, was “more sophisticated” than it used to be. Colin Barnett ended the week, and his campaign, admitting he was uncomfortable with the preference deal. And no wonder. It acted as an amplifier for Hanson’s innate ability to dominate a campaign with her own special brand of right-wing crazy.

Imagine a federal campaign in which the Coalition is trying to focus on Labor’s economic policies while Pauline Hanson is alleging a Muslim-UN plot to poison us with fluoride dropped from planes. A preference deal, no matter how pragmatic, lends legitimacy to One Nation, and such views and will increase the likelihood they’ll drown out any other message — just like whatever chance the WA Liberals had of targeting weaknesses in Labor’s campaign was obliterated by the focus on One Nation.

There’s also a basic moral issue. There are, as both sides acknowledged during the first go-round with One Nation, certain thresholds that should not be crossed in Australian public life. One is race-baiting. The Western Australian Liberals abandoned that, and got no benefit. They’re left without either power or principles. Turnbull’s continued prevarication about preferencing One Nation reflects not merely a failure to grasp the moral issue that had been part of Liberal Party policy for nearly two decades but a strange indifference to the actual result in Western Australia, where the local party has been smashed to pieces despite Colin Barnett repeatedly professing he was unaware of any anger toward his government.

There’s one other thing: also on display in the last week was the extraordinarily thin skin of Hanson and the party’s senior staff. These are political players who insist they’re all about honesty, authenticity and down-to-earth straight-shooting — but hate being criticised with a passion. James Ashby has repeatedly tried to instruct journalists about what they can and can’t ask One Nation politicians, as if a party hack is allowed to dictate how the party should be covered. The ABC was barred from Hanson’s election wake on Saturday night, for the crime of Barrie Cassidy simply letting Hanson talk — thereby exposing her malevolent ignorance and reflexive spouting of her idol Donald Trump’s lies. Far from not covering Hanson, the trick to dealing with One Nation is simply to let Hanson open her mouth about anything other than bashing Muslims and watching her trip over her own feet.

In the aftermath, Hanson has variously blamed confused voters, Labor scare campaigns and Colin Barnett for the the party’s poor showing. Nothing, it seems, is allowed to interfere with these bigots’ delusions of political grandeur.