Answer to your question:
A politician who fits the definition of moderate need not oppose his own party (and run against his party's nominees - thinking of another good example).
The definition that a moderate must satisfy:
6. a person who is moderate in opinion or opposed to extreme views and actions, esp. in politics or religion.
7. ( usually initial capital letter ) a member of a political party advocating moderate reform.
The definition has nothing to do with opposing his party. Don't know why you can't understand our dislike for him. Over the years, you've shown dislike for lots of Republicans who did not toe the line. I don't think anyone has tried to prove how evil you are for doing this.