Yun Wulong's words weren't wrong, reputation is indeed ruined, launching a sneak attack on the younger generation is a problem and will lead to disgrace.
Even if it was just to rescue Guang Yue, simply knocking Ling Tianyu away would've sufficed as that too is good; there was no need to strike so hard. If it weren't for Ling Tianyu's strong physique, it's questionable whether he'd still be here now.
Even if the soul is immortal, it still needs time to be reborn, and starting cultivation anew, the Emperor Lineage would have to wait again, like in the first lifetime. It's too difficult.
Reputation being ruined is just the lightest consequence.
If the Emperor Lineage's people were here, it wouldn't just be one person taking action against him; the last remaining ancestor of Ling Tianyu couldn't possibly refrain from crushing him to death, and might even want to grind his bones to ash.
