It's cliche but ignorance of the law is no excuse. Citizens hear it all the time.
On one hand, I feel like it may be a little harsh, especially if the person was misled into believe they were obligated to vote as Mr. Joseph seems to be almost saying. On the other if you genuinely want to become a citizen of another country you should start by learning and respecting its laws.
Here is the NY state voter registration form. The first bullet under "To Register you must:" is "-Be a US Citizen;". Now that I've seen that I have a whole lot less sympathy for the guy.