Why do people have the power to fire you from a job based on if they like you or not?

They have ways around that like user said above. Unless they fire you for your race or ethnicity then you don't stand a chance against their corporate lawyers

That too can happen, but from experience, you can get on acting like a prick if you are good at what you do.
Like I wrote, its a balancing act.
At least if the employer is resonable and cares about a profit.
If its just an apparatchik excersising his power because he feels threatened or just feels like it there is not much to do.
On the other hand why would you want to work there, just fight them if they want to drop disciplinary discharge on you, in other case just walk and find a better job

I run an HR department at a non profit. Anytime someone is fired there has to be cause or else we open ourselves up to a lawsuit. I have had to work with employment lawyers in multiple cases where someone claims discrimination and the burden is on us(me) to prove it wasn’t. Not the other way around.

All right to work means is that a person ca choose whether or not to join a union. Since when is choice bad?

Since unions say that it’s bad because they lose money to spend on things their memebers don’t approve of.