I have always been a great believer in the principle that one works best when in a comfortable environment, and that means that within the bounds of decency and respect for one's colleagues, people should wear what they like.
I broke ground in one company I worked for by rebelling against the 'jacket, proper trousers, and tie' rule and suggesting that my team did the same. Nobody abused it, some people remained 'smart' and other went to 'smart casual' or even 'scruffy casual'. One of my directors told me that I didn't look like the head of a department, to which I replied 'good' which rather took him by surprise. My team were happier, more relaxed and productive, and it gradually spread through the whole department. External customers also appreciated a more relaxed environment.
As far as I am concerned the person who invented ties should have one firmly and tightly tied around his manhood or his neck until the blood stops flowing.