I see nothing wrong with it? Maybe his other car is an M?
My dad has corvette flags on the Denali my mom drives.
M3 Edition Grilles|Painted Reflectors|Matte Black Vinyl Window Trim|CF Performance Spoiler|35% Tint|19" Satin Black Avant Garde M359|Lux H8 V3
OEM Aero Lip|M3 Side Skirts|LCI Tails|M-tech Rear|Duke Dynamics CF Performance|Cyba 4.0 Black Chrome