One young man taking on an elite clan by himself can hardly be called cowardly. His values meant that he held the stability and prosperity of his nation higher than that of his clan, as he viewed the leadership of Konoha to be on the whole reasonable. The Uchiha clan on the other hand seemed to be acting out of pride more than anything, as any issues should otherwise have been brought to the negotiating table. The fact is they were planning a coup, something which Itachi's father confirmed in his dying breaths when he said he admired Itachi for being firm in his choice.