Can a U.S. citizen marry someone illigal and help ...

Of course two people who are in love can get married, however, because of the strict policy on immigration in this country, it is a very difficult process to prove that love to authorities. It is unfortunate to me that it has come to the point in our country that relationships need to be questioned in such a way, but it is a reality that we must face for now. After all, I have known cases where people try to pay their way into a false marriage in order to obtain a green card! Good luck. :)

Anthrogal brings up the most important point of this question.  Are they marrying cuz they're in love, or are they taking advantage of what marriage stands for by "illegally" obtaining citizenship?  I don't think love is part of this question.  It's just another way for someone taking advantage of the "loopholes" in our system.  If they're illegal in the first place, why don't they take the proper procedures to become legal?  If they can't (for whatever reason), then they shouldn't be in this country.  Plain in simple.