Relative strength of 很笨 and it's variants 很笨

I have heard my doctor refer to his employees on some occasion using the phrase hen ben (I assume he meant 很笨). When I first heard it I was a bit bothered. Should I be upset when this term is used or is this "light teasing"?

I've tried to evaluate this snippet a bit via research and came up with this discussion on Yahoo Answers. A wider variation appears on CantoDict (Cantonese/Mandarin). I guess there are varying degrees of insults and I'm simply curious to what extent this colloquialism applies.
You should be upset. 

I'd be upset if my employer said I was "很笨". 

很笨 pretty much means what you would think it means "very stupid". Teasing on the other hand would be something more along the lines of 傻瓜, etc — and depending on the tone you should be able to tell teasing from non-teasing.