The simple truth of it is that we live in a representative republic. Senators and members of the House are elected to represent the people that elected them. The people that elected Ted Cruz don't like Obamacare, so Ted Cruz is obligated to do everything he can to strike it down.
He's only worthy of criticism if he, like most of the members of Congress, stopped representing his constituents and instead represented himself.
"Those who produce should have, but we know that those who produce the most — that is, those who work hardest, and at the most difficult and most menial tasks, have the least."
- Eugene V. Debs (1855-1926), five-time Socialist Party candidate for U.S. President
"For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places."
Ephesians 6:12