So, is it sexist to describe someone's photo on a business website as 'stunning'? That was what barrister Charlotte Proudman thought when solicitor Alexander Carter-Silk made the comment to her on LinkedIn.

Before addressing that question, I should straightaway say that whatever one's opinion, it's wrong to send her abusive and offensive messages and a prominent newspaper shouldn't inflame the situation by referring to her as a 'feminazi'. She has an opinion. It should be respected.

And respect seems to me to be the key. Any sensible person will know that commenting on a colleague's appearance is to step onto dangerous ground. Some men believe women like to be complimented on their appearance. Perhaps this is understandable, given the amount of time and money many women spend on their appearance. In male-female relationships, more men are likely to be familiar with the phrase 'How do I look?' than women. But of course that doesn't apply to all women and even less so in the workplace.

You must respect what your colleagues find acceptable. Just as some people might be intimidated by suggestive jokes, others might enjoy sharing a laugh. My advice is to tread very carefully and err on the side of caution. In the workplace or when you are dealing with someone professionally, a person's appearance is not relevant to business. Then again, if someone likes to be complimented, it seems almost rude not to say something pleasant. There are no hard and fast rules.

It can work both ways. While I've never been described as 'stunning', women occasionally compliment me on my appearance (very occasionally). They might say they like my haircut or my new jacket. I am quite pleased when this happens. It's not saying they find me sexy, which I admit is unlikely at my age. That also opens up the possibility of returning the compliment in a non-sexist way. On the other hand, when I was quite a bit younger, a female colleague once squeezed my bottom. I regarded that as crossing the line. I would suggest one should never touch a colleague or business acquaintance except to shake hands. A reassuring touch on the arm, a hug of congratulations, a reassuring arm round the shoulder might all seem innocent but many find it an invasion of space or patronising.

To an extent, sexism is in the eye of the beholder but also in the intention of the perpetrator. Or to put it another way, context is everything. I agree with Ms Proudman that LinkedIn is not the place for comments on appearance. As she said, 'I am on linked-in for business purposes not to be approached about my physical appearance.' There are plenty of social contexts where such comments would be appropriate but for too many people the line between business and social is blurred.

I think Ms Proudman is also right that 'the eroticisation of women's physical appearance is a way of exercising power over women. It silences women's professional attributes as their physical appearance becomes the subject'. I have been appalled that the female Labour leadership candidates have been asked so many questions and received so many comments about their clothes, hairstyles and general appearance that the media wouldn't dream of directing to the male candidates.

Any of us can fall foul of a charge of prejudice. Even Ms Proudman. In responding to Mr Carter-Silk's comment, she said, 'Think twice before sending another woman (half your age) such a sexist message.' Which some of us might regard as ageist, given the implication that it might have been all right if he had been nearer her age.

I am aware that this blog may have offended some people. I have generalised about men and women. I have talked only about heterosexuals. None of us can hope to avoid all prejudice in our behaviour but we must try, if we are to get the best out of our professional- and personal- relationships.

This blog is written by Paul Lewis of the Winchester based marketing consultancy Seven Experience. You can connect with him on Google+ and LinkedIn