Why do employers fight workers comp claims?

Employers may fight legitimate workers' compensation claims because they are concerned that expensive claims could cause their insurance premiums to skyrocket, they want to discourage other injured employees from filing claims, or they want to protect their company's image.

Can you sue workers comp for emotional distress?

As you are only entitled to compensation for a diagnosable psychological injury and not for mere emotional upset or distress, you should ensure your workers compensation certificate contains a proper diagnosis with medical terminology.