accident tonight,advice please

my 17yr old learner driver maneuvered of a kerb on to a two lane road, after checking mirror signal manouver. However, a speeding car appeared from no where, glances the front wing of our fiesta, than a harder glance onto another car,jamming himself between the second car and a fence, the damage to the "aledged" (as he wont admit to speeding) was catastrophic, broken axle, smashed drivers and passenger wings on so on. BUT, on arrival of the police, the Pc stated that because my son was "joining" the traffic flow, however wrong the offending driver would be, ie speeding, in middle of a two lane road, built up area, just off a bend....it is still my sons fault as he was joining the road from a parked position.... even though he had all 4 wheels on the road and was progressing forwards. The officer intimidated both my son and me by stating if we wanted to take it to court, my son would automatically get 6 points and a fine.
Im at a loss, how can a speeding driver smash into two cars and its my sons fault.
Im yet to speak to the Learner Insurance Company we are with as to can we fight the fact that the police have said he is to blame, this will no doubt put up his premium while leanring, and follow him round for several years. Any help VERY much appreciated, and ask any questions youd like to. I do have several pictures of the incident, as well as google pics showing the area.
Id also ad that a witness in a car behind is prepared to state that the offending car was speeding. along with several Air Cadets who were at the scene as it happened.
thanks