Must we Disprove in order to Dismiss?

Just to summarize the last post, my thinking was along the lines that there are some proposals that are fantastic; and given that they are fantastic, you don't have to entertain them to dismiss them as implausible. The reason is that anyone can construct a non-verifiable, irrefutable, and consistent theory to explain a given phenomenon. And when you have one story that can fit the bill, you can construct another one, more complex and more fantastic. And one after that, and one after that, ad infinitum. The question is, is it rational to entertain every non-verifiable, irrefutable, and consistent theory? Do you have to disprove a theory in order to dismiss it?