Am I required to investigate a claim of “hostile work environment” because of abusive conduct even if no sexual harassment is involved?

Yes, it is necessary to investigate a claim of abusive conduct. Claims of a hostile work environment that give rise to liability are those based on a protected category—such as race, gender, gender identity, religion, etc. (see list of protected categories in your poster “California Law Prohibits Workplace Discrimination and Harassment”). If the hostility is not based on a protected category, the issue becomes more difficult.

Although not technically illegal, when an employee is being abusive, yelling, swearing, etc., that behavior creates a negative office environment that reduces productivity and can lead to a workers’ compensation stress claim.