About the abuse...And the sound argument (Question spoilers)

When Kamoshida said "Had he (the coach) not opposed me with a sound argument, I would've settled it with only breaking his star's leg"

What it means? In your opinion?

You can see in Ryuji's social link here that Ryuji says at first that Kamoshida had fired the coach of the track team, and then trained the track team to the bone while abusing them, and just because Kamoshida wanted to, he started spreading shit about Ryuji's parents...Which in turn caused Ryuji to go to him and raise his hand, Kamoshida then "defended" himself by breaking his leg...etc.

So maybe the coach's sound of argument was that the coach told Kamoshida he is abusing the students of the track team after he got fired? (though i'm not sure)

So the overall quesation i'm trying to ask: Was Kamoshida spreading romuers on Ryuji because of the coach who gave a "sound argument" against Kamoshida, or because he started to see Ryuji as a disobidient kid during their practices? and 2. In his social link he says kamoshida abused his team, and only then he mentions that kamoshida spread romuers on his family to the team. So, was he at first abuse them, then saw Ryuji's disobedience as irritating, and then told the team about his father?

If that's the case, what's the relation to the coach who got fired, to what happened to Ryuji?