Nido

Obito's nindo, or way of the ninja, was that his friends came before everything else, even the mission itself. It is unknown if this was an influence from hearing Sakumo's story, or just because it was Kakashi he was arguing with. By his answer to Kakashi's willingness to abandon Rin was to call Sakumo a “Great Hero.” Obito's saying then became:

"Those who break the rules are trash, but those who abandon their friends are worse than trash."

After his death trying to protect him, Kakashi would later adopt Obito's nindo as his own.