Why do I let things get to me so bad?

OK why do I have to be so dang sensitive? Sometimes I hate my personality. I have always been more of a follower than a leader, but something has come up at work that I have to stand my ground even though I am standing alone. Next week is Boss's Day and the office manager suggested that we dress up as gang bangers like our students. Now here we are fighting these students everyday to not were "their" colors and now we are going to dress like them, throw signs, take a picture of this and give it to our boss? I just don't get it. So I told the office manager that I do not agree with this. I do not want to glorify the gangs. She tells me we are making fun of them, like that is OK. Now this gift that we give our boss he can not display it in his office. Can you imagine the response if our students or parents saw it. I think we would lose some respect that we have worked hard to get. So after work today she tells me that even if I do not want to dress out that is OK but they want me in the picture. I feel so strongly against it I don't want anything to do with this project. I will not be in it at all. Now the only person that agrees with me is our campus probation officer, but did she speak up for me, nope. I am so darn stressed about all this. I really do not want to go to work tomorrow, but I can not hide from it, but I will go home after work and have nothing to do with the picture.