The former PM mocked the “caterwauling orgy” of concern in Britain about the prospect of Mr Trump winning November’s US presidential contest.
Mr Johnson said his old ally was not a “would-be dictator”, despite his role in inciting a riot which saw the unprecedented attack on the US Capitol building.
The ex-Tory leader also claimed that Mr Trump won’t betray Ukraine – arguing that his “sheer unpredictability is a major deterrent to the enemies of the west”.
Britain’s former top diplomats have warned that Britain faces “massive” security risks if Mr Trump defeats Democrat Joe Biden and is re-elected later this year.
Two ex-Washington ambassadors and a former diplomatic chief said ministers should draw up plans in the event Mr Trump were to end support for Ukraine and withdraw from Nato.
But in his latest column for the Daily Mail, Mr Johnson claimed the “hysterics” were unmerited as he offered a shaky defence of the former Republican president.
He mocked Church of England, the BBC and “much of the UK establishment” for a “caterwauling orgy of nose-holding abhorrence” – claiming Trump’s success in the polls had “driven some people to the brink of virtue-signalling derangement”.
The former PM also said “the global wokerati have been trembling so violently that you could hear the ice tinkling in their negronis” at the Davos summit in Switzerland.
Mr Johnson claimed he did not minimise “Trump’s egregious error” of encouraging supporters to refuse to accept the result of the last presidential election and the riot that followed on Capitol Hill.
Despite the legal cloud surrounding Mr Trump’s presidential run, he claimed the American people “do not believe that he should be debarred from holding office again”.
He wrote: “Reasonable people can see that Trump is not, actually, a would-be dictator, and they have come to resent what look like legalistic ruses to axe him as a candidate. The more frenzied the effort to cancel him, the stronger he becomes.”
And despite Mr Trump’s hesitancy to support Ukraine, Mr Johnson said “I simply cannot believe that Trump will ditch the Ukrainians” – pointing to his record supplying Kyiv with Javelin anti-tank weapons.
He said the world needed a leader “whose willingness to use force and sheer unpredictability is a major deterrent to the enemies of the west”.
Mr Johnson wrote: “If he does the right thing and backs the Ukrainians – and I believe he will – a Trump presidency can be a big win for the world.”
He added: “You can actually make a case – and I may as well make it now — that a Trump presidency could be just what the world needs.”
The former PM also claimed the Republican was more likely than Mr Biden to offer a post-Brexit free trade deal to the UK. “Trump is your man.”
Mr Johnson worked at No 10 while Mr Trump was president for around 18 months without getting any closer to a free trade deal with the US.