Yes, bullying is being an irresponsible citizen. Remember to use the golden rule, treat others the way you want to be treated. Treat everyone equally or how you would treat an adult or your parent, treat them with respect and kindness. Treating people differently due to their race, sex, looks, size, etc.. is treating someone unfairly. Therefore, treat others how you would want people to treat you and don't bully in person or online.
Hope this helps! :3