I think the simple answer is: it's both. Changes in attitude cause language changes, and vice versa. But the balance of these forces isn't necessarily equal, and it may tip from one side to the other at different times in history. I would speculate that, in a society with a sustainable pattern of moral 'growth', more importance is placed on improving our ideas (through open discussion, taking in a wide range of perspectives, including those we find disagreeable) and allowing most language changes to flow organically from that. If the focus shifts too far towards trying to directly influence what people say (at the level of words/phrases), we risk stunting moral progress by encoding the status quo as dogma. Which, unless we are sure we already have the answers to all future moral questions, would be bad.
I can only speak from my own personal experience but yes! Absolutely 1000% yes. That is exactly the point and the intended goal of reclaiming the term.
The parent chose the usage of gay as an example of one direction of the push and pull of "language influences norms" and "norms influence language" but that dynamic only really applies when language develops naturally. When people start purposely influencing language then that goes out the window. Reclaiming the gay, f*g, queer, etc. was and is an active effort by the LGBT community and allies to directly influence norms through language.
Language and culture are intertwined like electricity and magnetism. Clear causality is only approximate because it always goes both ways, and solutions have to tackle both fronts.
I also noticed that gender neutral nouns and pronouns are more common in writing (for French and German). Again, that's a good thing.
The craziest example I have is the term "useless mouths" in Nazi Germany. Imagine if your group had that label. I'm certainly glad it's not in use anymore.