The most important thing to know about Republican attacks on people who don't pay income taxes is that many of the people who don't pay income taxes believe that they do, in fact, pay income taxes. I tried to make this point a while ago and apparently thoroughly botched it, as Jonathan Chait explained: "Most people make no distinction between 'income tax' and taxes, period." My guess is that a ridiculous majority -- 80%, 90% something like that of those who work but pay no income tax believe that they do, in fact, pay income tax.
If that's the case, then GOP rhetoric here isn't necessarily directed at rich or even middle class (income) tax payers; it may well be directed especially at working class people who don't actually pay income taxes but believe that they do. Indeed, for all I know low-income folks hear the "half of people don't pay income taxes" rhetoric and believe that it's about how working class people do pay taxes while the rich find ways to get out of it. And I say "for all I know" -- but you can be sure that someone is polling and focus-grouping this stuff, so Republicans who are pushing this line are working from evidence. Class warfare, indeed -- but class warfare in which Republican politicians manage to align themselves with virtually everyone who is listening to them, against an unspecified "them" who is getting away with something.
So: hey, pollsters! Could we get some actual facts about how many people think they pay income tax, and who they think doesn't?