This is the opposite of rigged. It's like arguing that getting rid of hackable voting machines means you're stopping efficient modern forms of voting.
Mail-in is a system that has more opportunity for fraud than any other, and the dems push it along with banning voter i.d requirements and signature verification -- that's not a coincidence and trump is making sure this can't be an option.
Vote in person or vote with an absentee ballot that obligates you to prove who you are. That's the choice.