Qin Wushuang was not narrow-minded to seek revenge because of one word. It was because after careful deliberation, he felt that this battle was unavoidable.
Regardless, since these five perceived his identity, certainly they would nag him unwaveringly. Even if he chose to shrink back, there would not be any leeway to turn around.
Compared to allowing his enemies to be in a tangle with him, it would be better to strike first and gain the upper hand.
By killing these five people, even though he would be offending those three dragon clans, at least it could serve to intimidate those guys that began to get restless. To some extent, it might not be a bad thing.