The flag only represented treason when the South lost. Up until then it represented freedom from the oppressive North, a North that wouldn't let them govern themselves how they saw fit.
I can't believe we're still dealing with this strawman. I also can't believe you don't see the irony in your own statement. The people of the south wanted "freedom" to deny freedom to others, and you're OK with that?
When some folks finally got enlightened enough to realize that the ownership of human beings is just plain WRONG, a majority of the citizens of the US (which is how our representative democracy works) convinced their legislators and President that "how they saw fit" should be outlawed. They way we effect change in this country is through legislation. If an Army base were to be attacked today for the reasons that Fort Sumter was shelled, we'd call it terrorism. So, yes, the flag was treasonous on the day it was created, and continues to be so because of the "ideals" it represents.
The southern states only considered this "oppressive" because an end to slavery meant lower profits for slave-owners. This is clearly outlined in their secession statements.