Propaganda doesn't totally rob people of agency free will (more accurate term), if it did this site wouldn't exist. People do have the capacity to develop critical thinking, skepticism, and a basic curiosity about the world that allow them to develop some resistance to propaganda.
You can hold people accountable for failing to even attempt to do this.
You don't need to emotionally judge someone who is malicious to want to stop them from doing harm. I don't see how us being against nazis is incompatible with thinking that we could have ended like them in their shoes
I think there are certain "turning points" in a person's life where they either go down a dark road or they don't. I definitely had a point in my 20s where the far right seemed tempting but I didn't go there, it's the easy option, actually learning about the world is harder. I reserve my right to judge people who did.