Yes, but it takes more effort, which is a significant motivation for the mechanism of voting.
That's true, but downvoting without comment is especially harmful to new contributors, who might conclude goodness knows what from it. ("Does Less Wrong hate me? Do they regard all meditation as woo? What's going on?")
EDIT: Oh, apparently this happened while the article was in Main, and in that case I'd have approved of the downvotes even so. I only came across it in Discussion, though.
http://www.sciencedirect.com/science/article/pii/S1053811911006008