CONFEDERATE FLAG,RACISM?

o.k. so why do people say the Confederate flag is racist? If your against it,then don't even answer.I still fly it to this date on my car and on the front porch of my house,oh and i have 2 in my room,but why do people always give me **** about it and complain? oh and ive done PLENTY of research on it and i heard not one thing about racism!