"Organized voting blocks" who demand 100% ideological purity end up being completely politically irreverent.
You nailed it. Libertarians don't understand politics. They don't understand, or can't accept, that political power is ALWAYS -- did I say ALWAYS? -- gained and held by one part principle, one part compromise, artfully mixed.
The Republican Party is simply a coalition of the center-right in America. It's not gathering of pure-souled libertarians, conservatives, pro-lifers, whatever: it's a political party. It's function is to KEEP POWER AWAY FROM THE OTHER GUYS.
Participating in politics is A TACTICAL ACT, not a religious devotion to be accomplished with utmost purity. In every vote, make the choice most likely to lead to the best outcome (which is not necessarily the same as voting for the person you like the best). The concept of a protest vote is the intellectual equivalent of the buddhist monk who burned himself in front of the embassy: interesting exercise, but no practical outcome in this universe.
Right now, the GOP has "compromised" so much to the Left that they sound like Democrats did 20 years ago. How "artful" is that?