I participate in larger SE sites, and I have clearly seen how helpful downvotes are there. Authors of questions and answers get immediate feedback of what the community thinks of the post compared to other questions and answers. Newbies who post half-authoritative answers to "test the waters" get quick and honest feedback, and are often pointed in the right direction; those who do more than just lurk either learn the rules and become useful members of the community, or they leave or are forced out. Larger SE sites have plenty of users, and lots of questions are asked every day.
Our site is, well, different. I think of it as semi-functional. First, our subject matter, amateur radio, is in many ways a mature technology that is past its golden age. That's the narrow view. The broader view is that amateur radio is a broad pursuit and subject matter, and there are many interesting facets to participate in or learn about. Unfortunately many of ham radio's sub-communities are badly represented here, as evidenced by the questions asked in the last year or two. For instance I haven't seen many questions about contesting, QRP construction, VHF/UHF, satellites, VLF, DXing, etc. In many cases we have experts on such subjects in our community, but the questions just don't come in very often. It was not always thus; in the early days of the site, questions about these subjects were more common, and attracted many answers and vigorous discussions. It seems that once the "low-hanging fruit" were plucked during the site's early days, most of those users left.
The Area 51 statistics for the site back me up that something's not quite functional about our site: we have lots of users and visits, but not many questions or answers.
But it's not all bad news. We have a decent-size community of people that check in regularly or semi-regularly, including many astonishingly well-qualified experts, and the basic subjects such as electronics and antennas are quite well covered. Some sub-communities are well represented: ask a question about SDR here, and you are sure to get an expert answer.
So if our site is not exactly like the bigger SE sites that are healthy in every way, should it operate the same as the bigger sites? I believe @webmarc's answer makes the point that it's OK if we don't downvote questions and answers as vigorously as the larger sites, and I think I agree with him.
In particular I personally try to not scare off the newbies, because we could use more participation, and any improvement in the small fraction of new users that hang around for more than a post or two could help. So rather than downvote a newbie's half-baked question or answer, I will often try to write a comment with constructive feedback. Unfortunately I don't think my efforts have helped much, but I'll likely keep trying.
I can think of an instance when an answer clearly merits a downvote, whether written by a confused newbie or not: when it is factually incorrect. We don't want to see misinformation propagating here.
(My understanding of best practices here is evolving, and my opinion may well change in the future.)