Once in a great while, a politician does something which gives us hope for the future. Unexpectedly, the latest is a Conservative lady. With a minimum of encouragement, she agreed that it was "highly probable" that, in her twenties, years ago, she got wasted with Nigel Kennedy on a dancefloor. I could get all teary-eyed about this heartening response. It feels like the British doing the Obama hope-y, change-y thing.

Louise Mensch is a new Conservative MP who, by the current, Milibandish standards of MPs, has a colourful background. She worked in her youth for the record company EMI and has carved out a career as a novelist under a previous name, Louise Bagshawe. She is also rather hot on the subject of journalistic propriety, and as a member of the Commons select committee on culture, media and sport, gave the Murdochs a memorable grilling a couple of weeks ago.

She received an email from a soi-disant investigative journalist, calling himself David Jones. (It is worth saying that this person proved not to be the David Jones who writes for the Daily Mail, and the real author of this email, and the publication he writes for, have not been identified). This person confronted her with three allegations. First, she took drugs and danced while drunk in front of journalists. Secondly, she was sacked for writing a novel "of a sexual nature" on an EMI work computer. Thirdly, she made derogatory remarks in her novel about her line manager.

Ms Mensch replied that not only had she used her line manager's name for a minor character, she had used the names of other acquaintances. As for writing the novel, actually she was sacked for leaving early, not turning up at all, and turning up inappropriately dressed. As for the drugs, drink, journalists and Nigel Kennedy allegation – "This sounds highly probable ... I am not a very good dancer and must apologise to any and all journalists who were forced to watch me dance."

Magnificent woman, and her response, which she published herself, is within the best, eff-off Tory traditions. In December 1824, the Duke of Wellington had a letter from a well-known blackmailer, Joseph Stockdale, saying that a famous prostitute of the day, Harriette Wilson, was about to publish her memoirs of her famous clients, including some letters from the Duke. His response was instant: "Publish and be damned."

More recently, the politician and diarist Alan Clark got away with something truly deplorable by just refusing to engage with denial. The New Statesman was told that, as a minister, he had referred to sub-Saharan Africa as "bongo-bongo land" in a departmental meeting. They challenged him; he merely said: "Well, I don't remember saying it, but it sounds rather like me." The scandal failed to ignite.

By contrast, almost every genuinely damaging political scandal emerges when a politician denies something disgraceful; goes on denying it as the media enjoys itself; produces a totally ludicrous explanation when proof of the behaviour emerges; finally admits it, and has to resign.

In this situation, it hardly matters whether anyone really cares about the bad behaviour. Almost certainly, the journalists writing it aren't remotely concerned. As I write, one Sunday red-top's lead story is that the Today programme broadcast some foul language to its audience which, we are told, "includes children". The foul language, in fact, were the words "bollocks" and "bullshit". I would be surprised if there were an eight-year-old in the country unfamiliar with these words; still more so if any of the tender souls who actually write the Sunday Express were genuinely shocked to hear them.

A comparable hypocrisy is often apparent when journalists address stories of bad behaviour. Is "David Jones" so shocked and surprised that, in the early 1990s, now-respectable people sometimes got drunk and even occasionally took drugs before venturing on to the dance floor? Is it so very horrifying that someone wrote a novel on their work computer? I can see that people might prefer it if their MPs didn't take drugs while they were supposed to be working on their constituency casebook. But if "David Jones" had gone ahead and published this non-story about Ms Mensch, would a single one of his readers have cared about things that had happened nearly 20 years ago? Of course not.

When hypocrisy meets hypocrisy, they unite, and egg each other on. Mr Ron Davies joined the ranks of the immortals by his acts of denial. The MP was discovered in the middle of the day in a gay cruising spot by a motorway. Challenged, he first denied that he had ever been there. Then he said he had been going for a short walk. Then he said, unforgettably, that he had been "watching badgers". What these blameless nocturnal animals had to do with anything, God only knows. But by the end of the affair, Davies would have been much better off saying "Yes, I'm gay, and I just felt ... I don't know ... extremely randy at the time".

What is so richly heartening about Louise Mensch's response to these allegations is the sight of an honourable, strong-minded, responsible person standing up in her own name against a mean, rat-like prig who hides under someone else's name. Pretending to hold moral attitudes while writing under a pseudonym, or pretending to be someone else, is contemptible enough when it happens in the online comments under an article, or in a blog. When it is engaged in by someone claiming that they want to get at "the truth", the author deserves to be hauled out and publicly shamed.

Ms Mensch may have done British public life a grand favour. For years now, people with an ordinarily colourful life may have been discouraged from entering public life for fear that a past episode will be held against them. Others, already in public life, have been persuaded that they ought to lie, and conceal, and deny everything to the very point of being drummed out of office by a red-top campaign.

With four words, Ms Mensch may have changed all that. I genuinely hope that the next time a politician is doorstepped with some marginally discreditable episode from his or her past – one which obviously creates no real problem for their ability to do their current job – they have the nerve to reply as she did. "This sounds highly probable". Now bugger off.