taxing, it is your brother's decision to not go further, which has to be respected. Unfortunately, all that does is reinforce it into the mind of a bad driver that they can get away with it 'if they offer a tenner'.
It doesn't make the bad driving go away, but points on the license and a loss of no-claims is a better deterrant IMO and might just make the prats think about their responsibility towards other road users.
It could do that, or the accident might have shook him up a bit. I think that when turning out of that road (if not out of every road) he'll now check whether there's a bike coming.