I think it goes back farther than that. The question should be: who did Aguirre offend?
It started with the chief's letter of reprimand to Aguirre for "using profane and threatening language toward his subordinates". From the article:
Aguirre called supervisors in the South Central patrol division, which he oversees, "sons of bitches" and "lazy bastards,"
Reading between the lines, it appears that Aguirre appealed to the Civil Service Commission, using the "everyone does it" defense. Bradford was probably asked if "he ever used profanity" in that context.
Since he didn't use the classic Clintonism ("I don't recall"), he really had no defense when contradicted by his own subordinates. So, Bradford was hoisted on his own petard.