That doesn't seem so hard. Per this article:
> That meme — which Larry didn’t create or alter...
> Weems admitted in a later interview that he knew at the time of the arrest that Larry’s Facebook post was a pre-existing meme that referred to an actual shooting that took place in a different state, over 500 miles away…
He didn't create it, the meme was accurate, and the cops knew that. Every bit of the conduct they attempted to punish was clearly legal, and they knew it.
The opinion you reference is at https://ww3.ca2.uscourts.gov/decisions/OPN/23-7577_opn.pdf.
"cannot alone establish Mackey’s knowing agreement" clearly indicates that things would have been different if they could have established that conduct.