The way I see it, Suo honored Nirei by taking the fight seriously. Pity is a form of disrespect. He saw him as an equal and treated him as an equal, and Nirei is always saying he wants to be on par with everyone else. He lost simply because he isn't on the master's level yet, that's all.
In my opinion, the worst thing Suo did that day wasn't going hard on Nirei, but laughing in his face and telling him they were never friends. That it was all an act, a total farce. That was the real cheap shot. Because we know it's not true, and we know he said it just to hurt him. If we're going to have a punitive fistfight, this seems like a much more valid reason.
PS: I absolutely love that it was Sugishita who got Sakura back on his feet. I really like that he's finally letting himself get more involved. Now I have no idea how I'm going to wait for the next chapters. Suo, I miss you! (╥﹏╥)
Based on what little we know so far, I don't like these people one bit. It feels like a straight-up criminal organization, which I get. They have their business, their secrets, okay. It's just that I hate people who mistreat our boys, no matter what their reasons are And did you notice they warned everyone within a one-kilometer radius except Suo? They know that if they let them meet, Suo would eventually end up choosing Furin. To hell with their town.