It depends on how someone is registered. In many places getting a driver's license automatically registers you. So it depends on whether the illegal registration was intentional, or happened automatically.
Then we need to consider the harm done by illegal voting. Voting is a statistical process and the harm caused by a single bad vote is small. In fact the small effect of any individual vote is why it is so difficult to get people to vote in the first place.
People complain about any attempt to change voting registration rules because it is possible with any change to predict how it will change the outcome. Whichever side will lose votes will complain.
I have yet to see any evidence of widespread illegal voting. Seems low on the list of concerns.
Maybe I'm naive, but I *have* to believe that residents -- whether legal or otherwise -- not eligible to vote would likewise not be eligible for any sort of automatic voter registration.
Then again, I wouldn't think they'd be eligible for ANY type of voter registration.
Regardless, the integrity of the vote should be protected at all cost.
If that means my candidate loses, so be it.
If that means bringing photo IDs and voter registration cards to the polling station, so what?
Seriously, who is put out by that?
Bottom line -- we cannot pretend to cherish or participate in any sort of meaningful
democratic process with any such vulnerabilities in our voting process.