Love it or hate it any self respecting hipster fashionista will recognise the Diesel BE STUPID campaign from a mile off. Personally I really love it! I think it's such a fun, clever idea.
The idea is based around that one sentence that makes your passion seem ridiculous and can crush your hopes and dreams, moreso if it comes from your mother. 'Don't be stupid'.
The idea is basically to stop thinking so much and just do it, whatever 'it' may be. It's the thought that trying to think smart limits your thinking because it caps your imagination. Watch it, embrace it, do it.