Very frustrating that so many people can't or won't separate legal and illegal immigration

I have had occasion recently to engage in an immigration debate with a very sweet and very liberal person. I'm glad I did because suddenly the situation became crystal clear. It is all about guilt. She was arguing passionately about her family being immigrants and being treated badly as they tried to settle into this country. Her feeling was that there is a bias about anybody who is different. And, I have to acknowledge her feelings. There was unwarranted discrimination against many legal immigrants who came to our country in the early days. Still, it is very frustrating that so many people can't or won't separate legal and illegal immigration. Nor will they distinguish between refugees and immigrants. Legally admitted, properly vetted immigrants are the fabric of our country. Nobody disputes that. Let me repeat, nobody disagrees. It is a point we can all agree about. Where our paths separate is the other people, those who are not vetted, health screened, or even identified. Why, why, why do you want them in our country? Is it guilt, ignorance or misplaced ideology? There is no common sense argument for admitting people we don't have any way of identifying. At least none that I can think of.