Employers are obliged to protect staff from bullying and harassment. Generally, this is in terms of discrimination, but may include anything from their favourite football team, what a person wears, their hobbies or their mannerisms.
Employers are obliged to ensure that the work environment is mentally safe for everyone and therefore free from bullying and harassment.
Prevention is better than cure and employers can be held vicariously liable if they don’t take adequate steps to prevent bullying and/or harassment taking place.