Should it be against the law to marry an illegal alien?

You constantly read on here people wanting to know how to give their spouse legal status. Just today, I have read at least 7 questions all asking how to make their spouse or the parent of their children legal. Then they get mad because you tell them they can't and that they will be deported with a ban. What do they expect? If we changed the law to stop allowing illegals to marry American citizens, would it also decrease marriage fraud? Should marrying an illegal be considered aiding and abetting and be prosecuted? Is it aiding illegals on here when they ask if and how to make their illegal aliens have legal status?