Even if you're not at fault, you should apologize.
Literal
Even-if-たとえ not-bad-ても, should apologize.
たとえ + the te-form negative 悪くなくても ('even if (you're) not at fault') forms the concessive. 謝るべきだ uses ~べき, the formal/prescriptive 'should, ought to.' Advice-register sentence, common in Japanese discussions of social harmony.