In case you were wondering, Dred Scott didn't say "that the Constitution allowed slavery because of personal property rights," when "That's a personal opinion. That's not what the Constitution says."
In 1856 the Constitution said that slavery was legal, as it had from the beginning. Article I, section 2, paragraph 3, excluded slaves from being fully counted in the census (they were counted as "three fifths of all other Persons"), and section 9 provided that Congress couldn't prohibit importing slaves until 1808. Not all of the Constitution's drafters approved of slavery, but they couldn't get the votes to outlaw it, and so it is undisputed by people with, you know, actual brains that prior to the Thirteenth Amendment, slavery was constitutional.
I was going to write up a post on what Dred Scott did say (some cases, I suggest people read if they want to know what they say, but I've read novels shorter than Dred Scott), but Professor Balkin has beaten me to it:
The problem with Dred Scott is that the Court reached out to decide something completely unnecessary, that blacks couldn't ever be citizens, and it also held that in order to treat southern whites equally with northern whites, they had to have the right under the Due Process Clause to bring their property (slaves) into federal territories, which meant that the federal government couldn't ban slavery there.
That last is a reference to the Missouri Compromise, which some of you may remember from high school history.
Okay, two more comments. One, Bush went on to say, "The Constitution of the United States says we're all -- you know, it doesn't say that. It doesn't speak to the equality of America." (My emphasis.) Excuse me?