Unless a specified level of hearing ability is part of your job description...then dismissing you for your hearing disability is most certainly discriminatory. Ask your employer for a detailed list of your task requirements then take it from there. However, Dismissing someone for being unable to fulfil the tasks for which they were employed...this in itself is not discrimination.

Bullying and humiliation is unacceptable though. I hope that you are able to find employment where your skills are valued, and your work environment is more forward thinking.