"I didn't leave the Republican party, the Republican party left me."

Honestly, it's hard to really say what principles the Republican party is actually for these days, aside from catering to whatever the very wealthy and the ultra religious Christian types want, as well as the general defense of bigotry.

This is bad for the country not just because of what they want to push through, but also because without a functional choice of realistic alternate solutions to problems, we suffer. The left isn't always correct in its first answer to a problem - sometimes it takes a different perspective to come up with better ideas, or at least to critique and thereby give a better solution. But you can't have that when one party refuses to even admit that there are problems in the first place, be it with Climate Change, Network Neutrality/ISP monopolies, Income Inequality, the War on Drugs/Police Militarization/Mass Incarceration, Health care, etc.