He did not say the f word. I watched the rally.
It’s about 36 minutes in. I think he was talking about getting those factories back from Mexico and he said something like “Then you can tell them to go ____ themselves.” But the word was silent. Just mouthed. I was OK with it but I know people who hate it so I don’t use it except in very special circumstances, like when the carrots won’t cook or Mexico takes our factories.