It looks like the wiper has been incorrectly set (too high) and thus when the motor spins it is bringing the arm into contact with the paint.
I think you should have a good case of arguing that the arm was incorrectly positioned from new and thus caused the damage. Are the blades the standard blades? with the little Alfa Romeo script on it, or the more modern aero wipes? (I don't think the aero's have Alfa printed on them).
My reason for asking - makes it easier to prove that the blades are originals and thus not changed, especially if they look weathered. Having said that, there is often zero reason for removing the arms from the spindels whilst doing a blade change, the blades should just snap in/out.
Do you have any invoices with the car? I am wondering if there was some work in that area, thus requiring the arms to be removed (and then later incorrectly set)
Current Italian Cars:-
2004 Alfa Romeo GT 2.0 JTS
Previous Italian Cars :-
2003 Maserati 4200 Cambiocorsa
2006 Alfa Brera 2.2 SV JTS
1999 Alfa Romeo 156 2.4 JTD
2005 Alfa Romeo 156 2.0 JTS Veloce
2004 Alfa Romeo GT 1.9 JTD
2001 Alfa Romeo GTV 3.0 V6 Lusso
2002 Alfa Romeo 156 2.0 JTS