It's simple. Show us the fraud. Produce the Bigfoot. If they can't, there no reason to believe it exists other than as a vehicle of deception to achieve political advantage.
It really is as simple as that. If in-person voter fraud is a serious enough problem that it requires spending millions of dollars and potentially disenfranchising thousands of voters, then show us that it's happening. If in-person voter fraud is actually happening on a meaningful scale I'll be the first person to support measures to stop it.
No song and dance, no anecdotes, just show the evidence.