Yes, it is rude and inappropriate to pinch anyone, regardless of their neurodiversity or whether they forgot to wear green on St. Patrick's Day. Pinching someone without their consent is a form of physical aggression and can be hurtful, disrespectful, and potentially harmful.
It's important to treat all individuals with respect and kindness, regardless of their background or abilities. If you want to engage in a playful or lighthearted way on St. Patrick's Day or any other occasion, it's better to find inclusive and respectful ways to celebrate together without causing discomfort or harm to others.