What if they had first been knocking for quite a few years begging for a bite to eat and a drink of water and your response was to pull the shade down in their face? Do you think that makes them less hungry or less desperate?
Do you know how long it can take to wait for a proper visa? What if you were about to die while waiting? What if your children were about to die while waiting, and you knew there was food enough in that house for all, the people inside and also yourselves?
I can tell you they wouldn't be trespassing inside your house if you welcomed them in, what a funny idea. And no, they aren't "stealing" the bread, most of them work their asses off for it. And though you would be correct to say that it is wrong for them not to pay their taxes, they still worked for the money they earned so it's not "stealing".
And though yes, there are people starving here in America, that is a distribution problem; we have enough to go around, we have plenty enough to feed ourselves and plenty extra besides, so don't try to claim that what "illegals" are taking means that an American won't have enough. Yes they will; we are the richest country in the world, and our unwillingness to share doesn't make it right.