Summary: Arnold is no saint.
People whisper, speaking of secrets and who likes who. People also gossip like there's no tomorrow and nothing generates gossip more than the news that Arnold and Gino are dating. Arnold simply ignores them; he has never cared for rumors and finds himself caring even less so when they are about him. While Arnold is content to ignore it all and let them be, Gino listens with fascination and finds it extremely hilarious that people have issues with Loan Shark Gino dating Saint Perfect Arnold.
It shows their ignorance because Arnold is no saint.
Every time he sees the man who mugged him Arnold flexes his hands or makes motions with his arms, causing his old mugger to shiver. Iggy who Arnold was once so desperate not to be hated by is treated with complete and utter indifference. Nothing the genuine remorseful teenager can say or do can convince Arnold to ever forgive or trust him again. The vain woman Summer who plotted to use him to win a competition is treated with sheer apathy when they encounter by chance in another summer vacation and she apologies with sincere regret in her voice.
A saint would have confessed to knowing about the bet on when Arnold and Helga would date. A saint wouldn't have told Helga and unleashed her wrath on unsuspecting classmates. A saint wouldn't have let Helga convince him to make a secret bet on her discovering it and beating everyone involved up.
Then there is Alphonse Perrier du von Scheck and La Sombra who Arnold has openly admitted to hating.
A saint would have forgiven them all, a saint would have never been so annoyed on the insistence that Helga was the only person for him that he manipulated events for vengeance and profit, a saint would have never let hatred remain in their heart, and a saint would have never interested Gino.
Gino knew he wasn't perfect, accepted it, and did not want someone who was perfect. Simply because perfection was boring, if one believed that they were perfect than they could never grow. Someone too saint like would have been boring, too rigid, and be in the right far too much for Gino's liking.
Arnold was no saint and that fact excited Gino. He found his taunts to the man who mugged him hot, his sheer apathy and indifference made him intrigued that Saint Arnold had limits on forgiveness, and his sheer cunning at claiming vengeance and profit made him delicious for Arnold in ways he couldn't describe.
It was long after Hurricane Helga when he began to seduce Arnold Shortman. Arnold allowed it because realized Gino didn't see him as a perfect saint, saw his faults and still wanted him. It was far more comforting than anyone could have realized because Arnold's grand accomplishments (saving the city, rescuing his parents, etc…) made him seem daunting to some, intimidated others, and made him appear untouchable. It placed him on a pedestal and the simple truth of the matter is the true reality can never reach the height of someone's hopes and dreams.
It also helped that Gino was charming, suave and had a really cute butt. That Gino saw liked him for the good and the bad. Even if Gerald was concerned that Gino liked the bad more than good, Arnold and Gino are simply who the other wanted. That they don't know if they will last, if they will spend the rest of their lives together, or if this will be a High School romance that erodes in time is simply irrelevant.
Arnold ignores the rumors, Gino finds them hilarious, and regardless of what the future may bring both boys know that they really like one another and for now that is enough.
Author's Note: As mentioned before these stories serve as a challenge as to what I can come up with and I felt the urge to do something completely different with Arnold and Gina just fell into place.
I head canon that Arnold hates Scheck, assuming that Jungle Movie will give plenty of reasons to hate La Sombra, and the rest simply developed as I was writing the story.