It is not a sin to raise taxes, nor is it a sin to lower them. The Bible neither condemns socialism (in its ideological form; its implementations have had instances of corruption) nor prescribes democracy. Gun control is not a Scripturally-backed concept, nor is the right to own guns.
Whether it's "Republican", "Democrat", "Libertarian", "Conservative", or "Liberal", none of these ideologies can or should be construed as shorthand for "Christian" -- or for "non-Christian."
When we speak of "God and country", there is an awful tendency to conflate the two. It's by grace we are saved, not by works -- works such as voting for candidate X. That unfathomable grace is given us by Christ alone, and no human authority can grant it or approach it.
Yet often it seems Christians fight harder over human governance than over Jesus's lordship. We boldly declare that the Church "needs to stand up and fight" on taxes or healthcare or wars, when the Church should preach salvation to the lost, minister to the needy, and teach God's Word to believers.
And we get mean sometimes; we draw lines in the sand and declare that anyone is either for or against us -- and by the way, God is clearly for us. So we shout louder and point harder and dig up all the nasty stuff we can about their people on the other side of that sand-line, hoping to make [the filthy rags][1] of our people look better than the filthy rags of their people.
We start to look like the Jews who rejoiced at the coming of Jesus not as a savior from the bondage of sin, but as a political champion against Rome. We hold up the Omnipotent Creator as a weapon for our legislative desires and hope that He will save us from the perceived oppression of our fellow countrymen.
In doing so, we forget that Christ saved Matthew, a Roman tax collector (hated both as a tax collector, who were notorious for falsifying taxes for their profit, and as a representative of the occupying Romans) and made him an apostle -- and that He also saved and chose Simon the Zealot, a member of an anti-Rome militant group, as an apostle. American political confrontations may be harsh and mean, but to the best of my knowledge they are not characterized by the mortality of this clash.
Jesus did not redeem Matthew despite his Roman ties nor Simon despite his Zealot ties. Jesus saved both of them despite their fallen, sinful state of opposition to God.
Frequently the Pharisees and others tried to get Jesus to side with one party or the other of this conflict. The oft-misused passage about "render[ing] unto Caesar what is Caesar's, and unto God what is God's" is actually an example of this:
The scribes and the chief priests sought to lay hands on him at that very hour, for they perceived that he had told this parable against them, but they feared the people. So they watched him and sent spies, who pretended to be sincere, that they might catch him in something he said, so as to deliver him up to the authority and jurisdiction of the governor. So they asked him, "Teacher, we know that you speak and teach rightly, and show no partiality, but truly teach the way of God. Is it lawful for us to give tribute to Caesar, or not?" But he perceived their craftiness, and said to them, "Show me a denarius. Whose likeness and inscription does it have?" They said, "Caesar's." He said to them, "Then render to Caesar the things that are Caesar's, and to God the things that are God's." And they were not able in the presence of the people to catch him in what he said, but marveling at his answer they became silent.
The historical context here is one of a revolt by some Jews against the Roman government over a census tax that remained a "hot-button" issue.
Jesus is not evading the question here. He's dismissing it. Perceiving the desire of the Pharisees to brand him with a political affiliation, Christ refocuses with a challenge to the Pharisees: are you obedient in giving to God that which is already His?
Our struggle is not against flesh and blood, but against sin. Let's reserve our anger [for that which God hates][4], rather than human opponents.
And rather than preaching a political gospel that trusts in human candidates for salvation, let's preach the Gospel of Jesus Christ: the unchangingly-perfect God-man [who died to save His enemies][6], so that we could be called His people.
[1]: http://www.esvbible.org/Isaiah 64:6/
[4]: http://www.esvbible.org/Proverbs 6:16-19/
[6]: http://www.esvbible.org/Romans 5:8/