Compassion for people in need is one thing, but the law is in place for a good reason. Can you imagine what would happen if immigration policy was eliminated so that anyone who could cross the border could do so? It would be the same as you opening the doors to your home to allow anybody to come in. That wouldn't just include those who want to visit, or a place to stay for the night, or maybe even a job from you. It would also include those who want to look around to see if there's anything worth stealing, and guys who are mostly interested in your 17 year-old daughter, or maybe even guys who are interested in your 8 year old son. But since you have no "filter" on who comes into your home, you have no way to know who these people are, and are endangering yourself and your family.
That's an example of security on a personal level. We need security on a national level as well. That's what the immigration policy is for.