Why does this meme depict the saving of abortion rights by voting for Harris (again)?
Because the more Democratic presidental terms there are the more nominees can reach the supreme court to overturn. Roe was overturned precisely because Republicans played that game of getting more judges on the bench
Additionally more dems in power increases the chance of a legislative victory on the issue
What "objective" measure implies Democrats are less hostile to BLM?
Listen to any Republican ever talk about BLM or make policy against "critical race theory" or "woke".
One of the parties declared open hostilities towards blm/crt/"woke" including via legislation. All of which they use to denounce black rights or history in some way.
On that measure Democrats are less hostile and it's an important one. You need to teach about the oppression to do anything about it