No, you really couldn't make it up. The politician in charge of the Commons committee reviewing the laws on prostitution is caught in a prostitution scandal. It is right for Labour MP Keith Vaz to resign as chairman of the Commons Home Affairs committee for the time being and for the Sunday Mirror to publish the story about his alleged assignation with male prostitutes. There was a clear public interest because this could have affected his judgment in the inquiry.

But beyond that, Jeremy Corbyn is right about it being “a private matter”. Nowadays, post Levison, the fact that a politician has engaged in extramarital sex would generally be regarded as a private issue unless he or she has made a big noise about family values. This a good thing: privacy is a human right after all. Even if the allegations are true, Mr Vaz has done nothing illegal. Even the “poppers” he was alleged to have taken are a legal stimulant.

But a lot of people seem to believe that Mr Vaz should now stand down as an MP simply because he was unfaithful to his wife. As was the case after the SNP deputy leader, Stewart Hosie, was caught with his pants down – literally, as it happened – there has been a clamour on social media and elsewhere for him to lose his seat too. Cheating politicians, it is said, are liars who cannot be trusted and therefore are not fit to hold political office.

Yet 40 per cent of marriages end in divorce and we surely can't hold MPs to standards that the rest of society does not observe. People have always had affairs. For many people the sexual urge is so strong that they will risk almost anything to satisfy it; and not just heterosexual men. Those moralisers who condemn the likes of Mr Hosie seem to forget that there is another woman involved in extramarital affairs and that they are often married, too.

And sometimes it is another man, or men. In the past there might have been rather more sympathy for a gay politician caught in a sex scandal. Gay men have been victims of prejudice and have often been forced to deny their sexuality in public and conduct affairs in secret. There is less prejudice today but gay men should surely not be forced do disclose their sexuality if they feel uncomfortable about doing so.

This means, effectively, lying about it. It's the homosexual catch 22. Some married gay men, who come out relatively late in life, believe it is more responsible to maintain the marriage in form only and continue to live a lie. Some wives accept this; many don't. It's not for us to judge.

Of course, some people will condemn Mr Vaz, above all, for allegedly using the services of prostitutes. Some of the criticism has clearly come from supporters of what is called the “Nordic model” who believe that the buying of sex should be illegal. But this story vividly illustrates the problems associated with changing the law to criminalise men who purchase sex.

There is first of all an assumption that the services of prostitutes are only sought by heterosexual men and this is clearly wrong. Some women use prostitutes and many disabled people also seek out sex therapists. There is a large prostitution scene involving homosexual men. Why should gay men not buy and sell sex if the transactions are free and open and without coercion? Are we right to dictate to gay men how they should use their bodies?

I don't think we are. In fact, I can't really understand why the sale of sexual services should ever be illegal unless it involves trafficking, pimping, compulsion or other forms of coercive behaviour. The Vaz case – if the allegations are true – demonstrates why prostitution should be legalised and properly regulated. So long as it is underground, the sex trade will remain in the hands of the criminals and blackmailers.

The fact that someone with so much to lose as a senior married MP will allegedly take the risk of seeking the services of gay prostitutes surely shows how difficult it would ever be to ban sex work. It's like trying to outlaw sex itself. We should bring it out of the shadows and allow sex workers to conduct their trade freely and openly within the law. Gay or straight, it's not called the oldest profession for nothing.