I still can't see how the halo doesn't partially
block the drivers view. Imagine it right in front
of steering wheel in your passenger car.
F1 drivers are rarely concerned with what's immediately in front of their car. If they're passing, or being passed, it means the car they're worried about is beside them. When turning they're watching apexes (apecies?) which again, aren't in front of the car.
Sure, they have to be worried about oncoming walls, but those are fairly visible around the bar.
If you look at recent F1 cars, they have antennae and cameras mounted along the same field of vision that the halo is 'blocking', so the drivers are used to that being a bling spot. Perhaps smaller, but not as dangerous as putting a beam directly in front of a passenger car.