Jomp, you have a right to your opinion on depression and how it's supposed to be treated, but it's only that - an opinion. There are multiple ways to treat depression and some ways are better for certain people than others, and you're telling the other ways that they're doing it wrong and they should give up. Not exactly helpful for their treatment, especially considering the unstable moods people with depression tend to have. The proper way to state your opinion on this subject (regardless of who's right) would be "I think the best way to combat depression is by taking initiative at a lifestyle change, especially since this study shows medication is ineffective."
It's fine to express your opinion but as this forum is intended to be a support group it's important to be sensitive to its members.
You're right in thinking you'd get thrown out of the African village for insulting their customs. Maybe if you tried politely offering malaria drugs as an alternative and not an absolute solution?