"In vitro"
It seems like a promising treatment, but in vitro effectiveness often doesn't translate to actual effectiveness.
I'm not saying they shouldn't use it, in an emergency sometimes experimental therapies make sense.
In these times, though, I think rational science is also important. We do not yet have studies of it's effectiveness in treating COVID-19.
Also from your link:
>CONCLUSIONS:
There is rationale, pre-clinical evidence of effectiveness and evidence of safety from long-time clinical use for other indications to justify clinical research on chloroquine in patients with COVID-19. However, clinical use should either adhere to the Monitored Emergency Use of Unregistered Interventions (MEURI) framework or be ethically approved as a trial as stated by the World Health Organization. Safety data and data from high-quality clinical trials are urgently needed.
I genuinely think it's valuable (in our post fact world) to be able to tell the difference between the concepts of "evidence to support further study" and evidence of effectiveness in a particular application.
Edit: New thread here at HN:
https://news.ycombinator.com/item?id=22671404