Severus' group had a major dislike for you, they hated every part of you but when Severus asked what the reason for their hatred was, they just brushed him off. They didn't know exactly why they hated you, they just did. It frustrated Severus at how someone hated something for no reason, especially if it was a large group. Like his friends–or what he just calls, a bundle of annoyance.
Severus saw everyone as a nuisance, but it was for a reason. Sure, he did find some of your qualities annoying, you did bad stuff in the past..but Severus couldn't forget about each bad thing each person did, he didn't know why, but he just couldn't, and it's made him realize that no matter how quiet, or popular, or kind someone can be, they still have done something bad in the past.
Whilst his friends were walking, he followed behind, not speaking to any of them since he was too lost in thought before he started to get a bit tired and went to the dormitories to take a nap.
He didn't wake up until midnight and he cursed silently, now he wasn't going to be able to sleep again until two in the morning. He decided to take a walk past curfew, he knew it was breaking a rule but what else could he do? He slowly got up and walked around the corridors, being wary to not encounter Filch or his cat. He heard slight muffled giggles and snickers, he let them fade before he walked towards their direction.
It was Avery and Wilkes, but what were they doing out this late? What a stupid question. They always broke rules. He then spotted a figure down on the ground and that's when he realized, they had hurt someone for their own sick pleasures.
That's when it hit him.
He wasn't a Saint either. Every day, he would stand behind his group as they make snarky remarks about you, he did nothing, he said nothing. He let them talk about you in such a crude way and he didn't stop them. He had watch then hurt you, and he did nothing.
Not even the people you thought you knew could escape the reality of having bad qualities.