correctly adjusted headlights dont blind anyone
this is not completely true. fitting an HID conversion kit to a typical 'reflector' style halogen headlight can cause glare; if you try and direct the beam 'down' to minimise this, you'll probably have poor visibility! the problem relates to the change in 'focal length'; that is, the exact point along the globe where the light is emitted differs between a halogen globe and HID globe. this also relates to the orientation of the light source; in a halogen, the filament sits horizontally, left to right (east-west); in an HID globe, the 'arc' burns horizontally but forwards to backwards (north-south). as such, the beam pattern changes, and glare can result.
it is less of an issue with 'projector' style lenses. whilst cars like the 916 GTV and 155 have projector lenses, they were still designed for halogen globes. but if you fit HIDs to these cars/lenses, glare is much less of an issue compared with say a 147/156. regardless, the projector lenses in the GTV/155 are still not optimised for HID globes (but won't stop me from fitting HIDs to my 155!).
i'm no expert on this matter, but i do understand basic optics. so it is completely wrong to think that re-aiming a headlight can overcome glare in all cars
anyway, this is all old news, surely. conversions have been discussed in these forums many times, and the same info is being rehashed here. however, the video is good to see, and will hopefully highlight the issues to more people.