TP rocks, but probably saw this as a cheap way to get them off his back. While he’s a democrat, he is smart enough to abide by “shut up and sing” rather than piss off half his audience like most performers do. His lyrics are more populist than political.
Have to wonder how many people even knew just what they were signing.
I’ve collected multiple signers on guitar pick guards for my own personal collection. Other times I’ve seen venues do it for future charity auctions.