Okay, after watching the video twice I think I know what the fuck he's talking about. He thinks that you'll request a mail in ballot, go to the polls, they'll say you already voted, and then you triumphantly show the world that you didn't vote, you still have the blank ballot, and obviously they've put in a vote for Joe Brandon under your name, is what they've done, those bastards. He has done a terrible job of explaining his plan, aside from it also being a bad plan.
As a former election judge in Minnesota, I can tell you exactly how this would go in real life in that state (where, to brag a bit, we have a very progressive voting system that makes it very easy to vote, all the things Republicans hate). You'd get your mail in ballot, then show up to your polling place with your blank ballot. Then when you ask to vote, they'll say "yep, sure, come on in" and you can just go in and vote as normal.
(The rule is that even if you request an absentee ballot, you can still cast a vote as normal, and even if you have mailed it in, either they have already counted it and then the registration system will bar you from voting in person, or if you get there before it gets processed and vote in person instead, they'll toss it out when they get to it.)
Worst case scenario, the election judges see that you're carrying around an absentee ballot, and they'll ask you to get rid of it because no one wants ballots floating around a polling place that aren't valid. That's the only thing I can think of that would be cause for a Republican to make a ruckus, but... like... yeah, you can't just bring extra ballots to the polling place. And they won't scan into the machine because they're the wrong type. I really, really want to see videos of these people trying to catch the evil Democrats and then just, like, being treated normally though. (Even better if they raised a ruckus and then didn't actually vote.)