>I don't understand why it's so controversial among the pro-immigration crowd to say that people shouldn't come here illegally.
It's because the official green card process is [utterly ridiculous](http://reason.com/archives/2008/10/01/what-part-of-legal-imm...) and stacked against almost every prospective immigrant. It's one of those cases where the law has failed to catch up to the underlying economics of the situation: immigrants need jobs and the US has a need for cheap or highly specialized labour.
That is the process that needs to be reformed. Kicking out the people who are already in the country doesn't achieve anything other than waste more money and ruin more lives.