I got (what I believe) unnecessarily written up, can you read and tell me what you think?

I got written up for my fourth tardy in advanced 2 dimensional art, I told the teacher I was late because I was filling out National Guard papers and talking to the recruiter, he told me I would just be a bullet catcher on the front lines and I was useless to them. Now, shouldn't he get in trouble for saying that to a student? I really don't think I should get detention for a hour or so after school for deciding to protect his stupidity and the rest of America, should I tell someone?