In order for harassment in the workplace to be unlawful, it has to be based on characteristics of a protected class: race, gender, medical condition, religion, age over 40, pregnancy, etc. You won't be able to file a class action based on race discrimination unless it happened to you, but others may have a valid lawsuit. Rude behavior by a boss (calling someone stupid, etc.) is not a proper cause of action (claim) for filing a lawsuit.
The facts you summarize here do not suggest the applicability of class action standards. It seems like you had an abusive and unpleasant boss. That is generally not unlawful. The law will not protect yelling or harassment for perceived stupidity. Employees who were harassed about their race may have a basis for claim.
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