From what I can understand, the people trying to change bitcoin are Bitcoin core developers who want to remove a filter that up until now has been preventing illegal content being uploaded.

Correct?

So who's the one trying to change the hammer? The person who says that killing people should be illegal and everyone should have access to hammers, or the person saying killing people should be legal but hammers should be banned.

That's how I understand it but I'm new to this whole thing, started learning about it yesterday.