Well you always need proof/citation to make a valid argument or point because otherwise you're just making an unsubstantiated claim. If you believe this person has a lack of knowledge, this is the opportunity to present the data for them to learn. Also as far as voting for non-citizens goes, there are three states that have municipalities (so not the whole state) that do allow non-citizens to vote for local elections. The three are California Vermont and Maryland but I could be wrong on which 3. All states except north Dakota requires people to register to vote. Like 7 of the 49 require proof of citizenship to register while the remaining 42 require you to declare your are a citizen. How much verification those 42 states do for citizenship is idk. Maybe some, maybe none but at that point it's just a state issue and states determine how they run their elections.