Idealism vs. realism

Libertarians are often confused when it comes to politics. Should they fight for liberty in its ideologically purest form or practice politics as "realists", only focusing on those issues which can realistically be changed in today's political climate?

My favorite response to thoughts like these is as follows, in a quote by an anti-slavery fighter in times when slavery was considered the norm:

“Urge immediate abolition as earnestly as we may, it will, alas! be gradual abolition in the end. We have never said that slavery would be overthrown by a single blow; that it ought to be, we shall always contend.” /William Lloyd Garrison

This quote can be found in the great book For a New Liberty: The Libertarian Manifesto by Murray N. Rothbard (p. 18).