Can my employer reduce my hours for just any reason?

My GM recently tried to fire me over a 'voluntary" three page statement that was turned in to him by a customer. I believed the statement to be false and got the owner of the establishment involved. It turned out that the statement was from a customer/contestant of a contest of whom he(GM) was illegally giving free alcohol to. The owner of the establishment disagreed with the GM and overrode the GM's 'termination notice'. Since that day the GM has wrote me up twice: once for changing the schedule(I've made the schedule per his request for the last 7 months)without his approval. The schedule was constantly being changed before due to everyone's unwillingness to work and I had never been written up for it and I have proof that it had been changed before. The second write up was for someone else's actions in which GM claimed was my responsibility after telling me that same day that any/all authority had been taken away from me. How can I be held responsible for others if I am just a regular worker like them? He then revoked his request that I make the schedule and also reduced my hours. I have been employed longer than anyone else plus I have more certifications and qualifications than anyone else. Since all of this started I have seriously felt intimidated by the GM and he has created a hostile work environment between all the employees. Am I being treated fairly? Is this completely fair? Isn't this considered retaliation? What can I do about it?