So for a little bit of background, this group has been together almost 3 years now. We first started DnD with a homebrew campaign of mine in January. I was the DM for awhile and then we started a rotating DM cycle incorporating multiple editions and campaigns. I am not GMing the Stargate RPG, but a friend of mine is. I am the type of DM where I let people take things back so they did not happen in game if they only meant it as a joke and didn't intend for it to happen in game. My friend is not. If you say something as a joke and he thinks it's funny, then you just did it. We were creating characters and, with GM permission, made an engineer who would be the head of the SG team. He is also a bit of a prankster and has a lot of Jacks attitude. Some of the backstory is that I worked directly with Jack at the pentagon for awhile, so I picked up a lot of his habits. Think Jack but with a PHD in engineering. He also is from Utah, but pretends to be Russian as part of the bit. I was tasked with coming up with things that he does between missions that he is being accused of and has to defend himself against. Well I shoot my ideas over to the GM and he loves them. Then he decides to add a few of his own.
Some of the ideas I have are like rigging the intercom button in his office to play the song "I'm an a**hole" when he presses the button, but only the one in his office so base operations are otherwise unaffected. Or rigging our Tokra team members TV so it only plays videos of people doing the worm. His ideas are things like whipping out my d*** out in the middle of the messhall in front of 36 people and yelling "I AM 100% a D***". Or running through the medical ward naked yelling "I am the machine". I have already told him my character would not do that. So he decides to tell me that my character would. This throws me off because as a DM I know the number 1 thing you never do is tell a player what their character would and would not do. So, I tell him in no uncertain terms that my character would never do something like that. He proceeds to tell me that they are just accusations for my character to defend himself against and are not necessarily true.
Problem is, everything he is saying I would "just be accused of" is in places where there would be security cameras that would either prove or disprove those accusations and I would have no need to defend against. The security footage would either prove my character is innocent, no need to be called in to the base commanders office, or proven guilty which means just being called in to face charges. He is refusing to listen and insisting that my character would do these things which makes me think he is planning on bringing them up in within the next few sessions. I have already told another friend, who is in the group that if he does I will hand the GM my character sheet telling him, "Since you want to control my character so much, here is the sheet. Peace out. I will not be attending Stargate sessions from now on." My friend thinks I would be completely justified, but some part of me thinks I am over reacting.