I have seen many christians denounce other beliefs. Most of the time not other beliefs in particular, but in general. They say things like "Jesus is your only chance for salvation, convert or you will burn in hell". In my mother's church, a group of parishoners started the idea that the church needed to pray for the 'heathen jews' to "save their souls and hope God will show them the true way to heaven lest they burn forever in hell".
Those are not the norm and they give a bad name to Christianity. Jesus befriended tax men (who at the time were rather wicked), prostitutes, etc. He made numerous comments and references about NOT attacking others for their beliefs. If we were supposed to denounce other beliefs, Jesus wouldn't have ever gone to the gentiles in the first place.
And, as far as Judaism, Jews are still God's chosen people. That doesn't necessarily mean they will enter Heaven, but they are still the chosen of God. Calling them "heathen Jews" is definitely not a true Christian attitude.
Although, the Bible clearly teaches that there is only one way to Heaven, it does not teach that you should force your beliefs on others. It teaches to lead them, answer questions, etc... but above all, to live your life like Christ as that will bring more people to Christ than anything you could ever say. We were given free will for a reason.
It is true that probably 75% of Americans will say they are Christian (based on polls I've seen in the past... those may not be accurate polls, of course). However, if you really look at what they believe and if they are really followers of Christ, you'll find that only perhaps 20% of Americans really are Christians. A great quote I've heard in the past says -- "Going to church does not make you a Christian anymore than going to McDonald's makes you a hamburger." It's very accurate and true.
Darth Wong wrote:
In fact, in the last poll it was shown that more than half of Americans would flat refuse to vote for an atheist regardless of his abilities or his views.
I think that's incorrect. Consider the number of presidents who were not Christians. They were voted in. There's nothing wrong with an atheist for a president. There is also nothing wrong with a Christian as a president. Most likely, the wording on that poll was such that atheist was seen as someone "evil" or whatever. Not believing in God doesn't make someone bad.