His comments drew truths from multiple places, but as a whole, they are wrong.
You've got something like 40% of voters that are devoted to the Democrats, that won't consider a Republican. You've got 47% of Americans that don't pay income taxes, so lowering taxes doesn't affect them the same way it does others. Lastly, you have an entitlement class that will resist any change that takes government subsidies out of their pocket.
There's some crossover between the groups, but they are not a single group. Some conservatives make up that 47% that take care of themselves and would prefer to reduce the welfare state.