As a colleague I might think it's kinda funny or at least weird, but I wouldn't ridicule him over it. As an employer.. I dunno. It's not so much the look but the fact that someone who wants to wear that all day (especially at work!?) might be a bit flaky in some way. I guess also it's the look, because it might cause a lot of unwanted workplace drama. And if customers can see him then it might give them a bad impression of the company. I don't necessarily think it should give a bad impression, but you have to be practical.