Even for those that cling to the Bible, they recognize that it can be used to say anything.
The only way that can be accomplished is by playing Bible hopscotch. When taken in context, not only of that particular portion, but also of the character of God and the purpose of the Bible, it is quite clear that some things are wrong. However, many 'false teachers' very much like to take things out of context to support a particular viewpoint of theirs, and then various people who don't believe in the Bible point to them and say just what you said.
Sex, with someone other than your wife, is wrong. Reinna made it quite clear that not only is it wrong Biblically, but also in relation to society and the lives of those around you. I, too, have come to the same conclusion about sex. I first didn't engage in such a willful activity because God said "No", but as I began to question why God tells me to not do certain things, through His Word, I have gained an understanding that I'm not to do them because they are harmful, not only to myself, but to those around me. As for the rest of the points (Christmas, gambling, voting, etc...), Romans 14, as has been quoted several times already is very true. Also, there is a verse (I think it's in the last 4 verses of 1 Cor 10) where Paul asks, "Why am I evil spoken of for that which I give thanks?".
As another poster said, IT is a personal relationship with Christ and just like any true relationship, we do things not because we're supposed to, but because we want to and because we want to make our counterpart in that relationship happy.