Workplace harassment

There is a legal remedy for having to work in a "hostile workplace environment". This comes into play when the conditions of the workplace prevent an employee from performing the duties of their job in a reasonable manner. In such a case, a boss and/or co-worker creates an environment that is counterproductive for an employee to effectively function due to that boss's or co-worker's behavior, actions, or both. That having been said, these behaviors must be legally discriminatory. In other words, your treatment must be based on your inclusion in what is known as a "protected class". This means that your treatment must be due to your nationality, gender, disability, age, gender, and in some states, sexual orientation. Otherwise, while such behavior is unprofessional, it is not legally actionable.
As for your termination, t fact is that most work relationships are "at will". This mean that an employer can set the conditions of the workplace much as it sees fit. Accordingly, an employee can be fired for any reason or no reason at all. That is unless an employee;s dimissal violates the terms of a union agreement or employment contract.

Unfortunately, your manager *does* have a legal right to belittle you or harass you, and your workplace may legally be hostile. Employment is employment at will; that doctrine has many consequences, but the most basic one is that an employee has no right to a job and an employer may treat the employee any way they want. The employer can also put unreasonable restrictions on you, like to not speak to other employees. Another basic consequence of employment at will is that in the absence of a written employment contract to the contrary, you may be terminated at any time, for any reason, even when you did nothing wrong.
There are managers who are unprofessional and downright awful, and there are workplaces which are toxic, and your only recourse is to seek different employment.