Xifeng was indeed a man who would stop at nothing to achieve his goals, and his methods were quite despicable.
For example, he would relieve himself before Lin Zhen's cultivation spot, something an average Quasi-Sovereign would never do. Murdering someone might be acceptable, but such an act involved dignity and reputation, it's not something to use lightly.
But this was his way, his advocacy, to act with complete freedom. When taken to an extreme, it surprisingly aligns with the principles of the Martial Way, which is why he achieved what he has today.
Xifeng dispatched a person to the outskirts of the town, with instructions to perform all sorts of lewd acts in view of the spiritual space of the Sunflower Scar.
This was a sinister act. Everyone was aware of Lin Zhen's attachment to the Sunflower Scar, and once such a thing was done, no matter whether or not Lin Zhen later retaliated, it would surely leave a psychological scar.