This thesis is certainly wrong. If Romney had as many total voters as McCain had in 2008, he would have won. McCain didn't grab a big portion of the Hispanic vote, and McCain was a big proponent of amnesty.
Republicans never win when they try to out-pander the Democrats. The problem with Republicans and Hispanics is the Republicans let the other side define them as "anti-Hispanic" and "anti-immigrant." Columns like this don't help the cause, either.