Just remember that whatever industry you work in, word and reputation gets around. What would happen if your new employer hear of this?
See this is the kind of thinking I dont like.
How many people have told you about that guy at their work, or their boss, who is an absolute P***k (excuse the language). Like the kind of guy that sexually harrasses employees and makes everyone around him feel s**t.
Most of you. Either you know someone in that position, or you are, or were, in that position yourself.
So the question I ask to those people is, what are you going to do about it?
"Oh nothing, it will just make things worse. No I dont want to make waves. I might look for something else on the side."
And you know what? Thats why bosses like that get away with what they do, because nobody stands up to them. People dont magically get power over other people - those people have to give power to them. This is what is happening, and this is why I say, if a boss treats you badly, you make sure he knows about it, that his superior knows about it, that everybody knows about it.
This kind of thinking is why so many of these bosses still exist - because nobody tells them otherwise.
If you worry about what everyone thinks of you, you become a doormat. Yes its a small world and that boss probably has connections, but do I want to work for any of his connections either? If they are like him, probably not.
So lets turn the question on its head - what would happen if your new employer were to hear that you were badly treated at your old job?
Perhaps you could argue that your "loyalty" (nobody has any these days, neither employers nor employees) is to the company and not your boss, so performing poorly at your job to spite your boss is ill aimed. I would accept that. Perhaps it would still be a good idea to be professional and come into work on time and all that. However, I would never be civil or nice to such a boss. He would know exactly where he stands with me.