You forgot Ellis, Johnson, Parker, Rockwall and Wise counties. Percentage wise they voted Republican as much or more than Collin County in the 2004 election.
Here's an image that more accurately represents how the country voted.
I did my own little analysis of the map and here's the breakdown by county in the Metroplex on a Republican to Democrat ratio (R-D)
Collin.......72.4-27.6
Dallas.......50.0-50.0
Denton.......70.5-29.5
Ellis........75.0-25.0
Hunt.........72.4-27.6
Johnson......74.2-25.8
Kaufman......70.5-29.5
Parker.......78.3-21.7
Rockwall.....80.2-19.8
Tarrant......63.1-36.9
Wise.........76.0-24.0
Even at the worst in Rockwall county 1 in 5 voters were Democrats.
Oh, and in the eight months I've lived / been working in Collin County and the two years I was in Ellis County, I've never heard any use a derogatory term for Dallas. Insensitivity must be a Dallas thing....