How can I win a debate?

I have a debate tomorrow and I can’t think of many valid points to help our side win The prompt is:

The supreme court decision in the dred scott case of 1857 set a legitimate standard for the protection of property rights.

Im on the north side so we disagree with that statement. So far I have these arguments:

1. The constitution says that all men are created equal, so if men are equal, no man can own another man.
2. The jury was comprised of all slave owners who were therefore biased, and the bill of rights says that all men have the right to a trial by an unbiased jury, so the court’s decision is not binding or legitimate.
3. Europe already acknowledged that should a slave move to a free terrritory, they become free, and by not following that example, the u.s. Moves bckwards compared to the rest of the world.
4. The missouri compromise is a binding agreement prohibiting slavery in the areas scott lived, and it is within the power of congress to govern a territory within their discretion, so because they acted within the scope of that discretion, the court has no power to overrule their decision and make the missouri compromise unconstitutional.
5. At the time of the ratification of the constitution, ten out of the original 13 states allowed black men to vote, making them citizens of the u.s. Who are protected by the constitution and thus cannot be owned by another man.

Are they any good and are there any other points I can make to prove the prompt wrong?