Dumb ideas are valuable.
We develop filters to block thoughts from escaping our mouths or pens. Sometimes we repress thoughts and emotions, too, which means we block them before we consciously acknowledge their existence. Our filters are honed by what we view to be societally acceptable, and they allow us to fit in with the crowd a little more seamlessly. I'm not about to tell you to throw away your filter-- your filter is important. We can't be empathetic, respectful people without a little impulse control.
What I recommend is that we understand when and how our filters are valuable. We should also recognize when we're using our filters, as we often don't realize when we're blocking promptings from our true selves. Sometimes the filter is the obstacle, and I'm finding that in my creative life I have to observe when my filter decides to take effect and then tell it to go away for a minute. I think each of us has thousands of brilliant ideas every day, but many of these ideas are filed away into the "inappropriate" or "stupid" folders in the brain's file cabinet. A huge part of unlocking a deeper level of creativity is letting those ideas out. Often the best ideas are disguised as absurd, stupid, and offensive at first. When they're explored further, they can reveal themselves to be unique, mind-expanding, and valuable.
People want to consume art that surprises, stretches the mind, or shifts perspective. In other words, people want art to do something to them. Because people interact with society constantly, they're too familiar with what is socially comfortable. Art which is societally comfortable probably won't do a whole lot for those people. Therefore, creators of art have to explore less comfortable ideas-- freaky, funky, wacky, dumb, insane ones-- in order to do something to an audience. Many fear going to those areas of the brain, even when they're alone... But in the creative process, no one is harmed by putting dumb ideas on a page and following them down a rabbit hole.
I find it helpful to validate even my strangest thoughts when approaching a problem or crafting a story. It's not a fool's errand to explore those thoughts deeply. One of them might unlock something truly interesting.