I think you guys are overreacting to this particular statement. The fact is that it would be impossible to prosecute them as felons because they would have a right to a jury trial which is impractical for 12 million aliens. Plus, felon means they could serve more than a year in jail- do you think we have enough jail space for that? They can still be prosecuted and deported for misdemeanors.
Don't get me wrong- I fully expect Hastert and Frist to sell us out eventually. They just didn't do so in this statement.
With respect, I believe that you might be missing the point. If illegal aliens are committing a felony by being here, that is a continuing offense. And this means that those who help them remain here, are aiding and abetting a felon in the commission of his / her felony.