I know a bunch of Puerto Ricans from work and socially (both who live on the island and those who live in the States) and each one is a good person.
The disgusting "jokes" at Trump's rally went sour particularly because they piled on the disrespect Puerto Ricans already feel: Trump blocked aid after Hurricane Maria and threw out towels during his visit. There are many reported instances in the states of Puerto Rico drivers licenses not being accepted as American.
Puerto Rico's struggling economy is a direct result of American meddling. America gets its tropical fruits and sugar elsewhere now. There were huge federal tax breaks of Big Pharma to set up shop there. Congress ripped those away and, overnight, Big Pharma left. Hurricane and fires are getting stronger because of American-industry spurring climate change. A federal law requires all ships that bring goods to Puerto Rico be American in origin--this prevents Puerto Rico from trading properly with Central and South America. Housing is becoming unaffordable as the wealthy mainlanders bought up houses during and after the pandemic to telework from--driving up prices. While Puerto Ricans who live on the island don't pay federal income taxes (and don't vote in the Presidential election), they still pay the same payroll taxes (Medicare and SS) BUT only get a small portion of that back in the form of block grants, which run out of money quickly.
Overall, Puerto Ricans are a proud and passionate people. To call the island a pile of garbage was a step too far and they are pissed off.