They will get sued and they will lose, here's why:
In order to be protected by the fair use doctrine under parody, the work has to actually be a "parody" of the original work. They would have to have employees called "boristas" or basically make the entire business a parody of Starbucks' Mission Statement, business environment and franchise model. If you just put the name Dumb in front of the brand and even admit that you don't think Starbucks is 'dumb', you've effectively admitted on your own company FAQ's that you're not doing a parody of their store at all.
This will not end well at all.