It seems like a proposed study gets penalised if it doesn't also predict the direction of an effect. For instance, if I want to see the effect of a certain medication on happiness ratings, but do not predict whether I think they'll be decreasd or increased by that manipulation. Why is it considered unsound to run an exploratory study, i.e. one that doesn’t have a specific prediction (hypothesis) but simply wants to see what effect a certain manipulation has on another dependent variable (i.e. you have a hunch there's an effect there but don’t quite know in which direction it'll be)?
In other words, what exactly is the formal statistical principle that is violated if you run a study without formulating an apriori hypothesis? It seems that if you're happy to pay the 'penalties', e.g. use 2-tailed instead of 1-tailed tests and correct for all the multitude of tests, any exploratory result should be just as believable as those of a hypothesis-driven study!