In a decent community you don't get punched in the face for asking an ignorant or lazy question. Instead, you do not get any reward or positive feedback for it (upvotes, attention to the question). The default of decency is a neutral, respectful treatment to others; a floor of dignity. People can learn how to better contribute without being either subtly or overtly attacked or bullied.

I also give downvotes an expense, they cost points (they subtract from your account score), and I increase the cost as it makes sense. So a user must earn the ability to downvote through contribution. If the system has too much downvoting, you can gently alter that behavior by ramping the cost overall and individually (if a given user is prone to downvoting heavily, you increase their cost beyond the base system cost).

Thought experiment: You say that reaching below 0 is punishing and getting more than 0 shows that your question is good. You get feedback that you've done great work writing the question. How would it look like when the site relates to your feeling when writing and contributing to the site? Would it work even if you remove score all together?

Giving rewards result in people seeking awards. Which may seem like a wise thing but aiming for self confidence is way better. Which is obvious but may be good to point out anyhow.

If the system knows the item is rated zero, then why even give the option of downvoting at all? Conditionally remove the control and you remove the need to display an error message.

In other words, give them a placebo button: https://en.wikipedia.org/wiki/Placebo_button