1. We did this before with Reagan, it didn't work, it made the problem worse. Far worse.
2. The social security trust fund was spent on a bi-partisan basis, both parties agreed to spend it, did that make it right that we have nothing saved up for this program that was paid in to for a generation? We now have no money to fund it, it's broke.
3. We HAVE immigration laws. Every country has immigration laws. We are one of the few that does not enforce them. Mexico does. If we tried to enforce our laws like Mexico did, very few would get in.
4. Immigration (LEGAL immigration) has served us well as a country for a long time, we took from multiple cultures and formed what was called the melting pot.
5. What the new immigrants are doing is insisting we speak their language (press 2), insisting they don't need to really take on US cultural norms, and are staying balkanized. It's a bad recipe. Has failed everywhere it's been tried.
6. Allowing in multiple millions of fairly poor, fairly uneducated people FROM ONE CULTURE ONLY who have access to our modern welfare state will bankfupt us.
7. Allowing the chain (bringing family once the law is passed) migration that will surely follow will make us unrecognizable as a country considering all the points above.
8. What would be better would be to secure the border once and for all, make it so they could not get jobs or welfare benefits, and force them to have to deal with immigration like anyone else around the world who wants to come here, and certainly LOTS of people want to come to the US still. Everyone else around the world HAS to get in line, fill out forms, be checked out for criminal background, etc. and WAIT for years to come in. Why should we make it easier just to walk through our Southern Border, and suddenly you get rewarded for breaking the law.
PS - This is NOT racist in the slightest, that's going to be your "friend's" main argument. Don't' let him/her get away with it. I wouldn't want up towards 20 million Swedes, Italians, Poles, Russians, Chinese, or Canadians coming in either.