"Stupid" comments are one thing, "stupid" questions are another. With "stupid" questions you at least demonstrate a willingness to learn and not just spew political talking points, biases, etc.

I self-censor because of this and think we shouldn't mind. I end up writing comments I don't submit, but I consider the exercise worthwhile because forcing myself to write my thoughts out and then judging whether they're truly helpful/insightful teaches me what knowledge gaps I need to fill eventually and where I'm just falling back on preconceived notions/biases to form my opinions.

So if you think you'll be down-voted ask yourself why. If you don't know why, then re-formulate your post as question to understand others' reasoning.