it depends on which type
a) if its a friendly against a affiliate, or a feeder club, then u gotta live with it, but u can use FMRTE to change the setting and untick (annual friendly's)
b) if its done on a transfer deal basis, like when u wanna buy a player, and u add a 'arrange friendly clause", then it can be removed since its included in the deal.
c) i always let my ***. Man. handle these friendly fixtures, and then i add more, or remove some under my opinion. but these and be freely canceled anytime, but before the match starts (like 1 day prior).
well if ur irritated by the friendlies, u can go to team settings, and select "let ***. man. take over friendlies", and then every friendly match is taken over him and u can do ur job as normal.