1. "Reagan Democrats"
Uh, no. These voters did in fact exist.
2. High-income people vote Democratic (in general)
Depends on the region.
3. Low-income whites vote Republican (this one's more a matter of degree)
See above.
4. Black people are more homophobic than white people.
*The Emoticon that Must Not be Used* at your use of 'homophobic'.
Black people are more anti-gay marriage, although that might have changed given Obama's recent 'evolution' on the issue.
5. America is a "conservative nation"
This is the only 'myth' here that might qualify as one.