"Amnesty" is a bad word, so many supporters of comprehensive immigration reform have played oftentimes complicated word games to pretend that "reform" is not amnesty. Those who do that are simply trying to deceive. While we could argue all day long about whether what they support fits the dictionary definition of "amnesty", and arguing over terms may be something that those supporters intentionally try to do, what really matters is how "reform" will be perceived.
And, millions upon millions of people around the world will perceive "reform" as an amnesty. It will send a very clear message to potential illegal aliens that we don't really support our immigration laws and that if they come here and stay long enough they'll eventually get citizenship.
Opponents of "reform" should try to avoid getting into a debate about semantics. For instance, if someone rants about amnesty, a "reform" supporter would latch onto that and simply replay their talking points about "reform" not being amnesty. Instead, opponents should make the point above; most people will agree with the point above and will disagree with someone who tries to pretend that most outside the U.S. won't perceive it as amnesty.
However, the best choice is probably to just avoid the word "amnesty" altogether. Instead, use their word - "reform" - and then show how that "reform" won't work; see the comprehensive immigration reform page for some of the downsides.