Dear Head,
Since you have informed me that I am not to talk to you until "I do so properly" which you define as giving you optional honorific, regardless of my opinions on them, I am resorting to written form to present my case.
I am not opposed to calling you sir, and I have many times, so this is not a personal slight, but a matter of principles. My opposition stems from being told/ordered to call you sir
I am a great believer in freedom of expression in all its forms, one of which is speech. Attempting to control and limit others speech through demanding titles, which skews a whole conversation in your favour is a restriction of my freedom of speech.
If, for expressing myself in a way which isn't even rude, I am to be suspended, the system we function in needs to be changed. For example, I "have to" refer to male teachers as sir, but no such equivalent exists for female teachers, who I must refer to by their marital status, as opposed to the female version of sir, which is Dame. This shows our school is patriarchal and even the rules on student-teacher relations are sexist.
I propose a middle ground. I will, if you deem it an acceptable alternative instead refer to you as Headmaster, in place of sir.
The head agreed, and lifted the suspension.