(if you're confused as to why there is a picture of bacon here, a) keep reading but b) why not!? :)
1) "all things indeed are pure." in other words, if the Bible doesn't say something is sin, you can't universally define it as sin. if the Bible is silent on a particular issue, or gives freedom, or doesn't set forth a specific stance, then no Christian (no matter how insightful he thinks he is) has the right to declare it as sin for all people. there are plenty of things the Bible does say are sin, and pride is one of the most often repeated. as soon as you take any of your personal convictions and try to force it on others, you have become a proud pharisee. this includes areas like drinking alcohol, birth control, watching harry potter, eating bacon, playing cards, listening to secular music, using electricity (thanks amish! ... and no, i'm not worried about offending them. they shouldn't be using the internet anyway. :), etc.
2) "whatever is not from faith is sin." if you are personally convinced God doesn't want you to do something which the Bible is silent on, don't do it. for you it would be sin! the reason it would be sin is not cause the thing/action itself is wrong, but because, in as far as you are convinced, it would be disobedience to God, and that is sin. keep your convictions. live by them. just don't force them on others because then you'll have a much bigger problem than eating bacon and watching harry potter.
3) "it is good not to do anything by which your brother stumbles." that is, if the option is between using your freedom to do what you want and serving your brother, go with the later. we are given great freedom in Christ, not so we can do what we want, but so that in surrendering it for others, we may become more like Him. the Cross of Jesus proves without a doubt that serving others is more important than standing on your rights. but does that mean we have to stop drinking coffee, eating bacon, watching TV and using electricity just cause it might stumble someone?
4) "do you have faith? have it to yourself before God." to serve others with our freedom doesn't mean that we become as strict as they are. it does mean that we use our freedom with discretion and readiness to surrender it for others. the principle is not "if this might stumble someone somewhere, i shouldn't do it." love doesn't exist in "theory", only in practice. the principle is: "if this does stumble the person i'm with right now, then in his presence i will refrain." use your freedom in places and ways it won't stumble others (at the least just before God... it won't stumble Him if you eat bacon. :) does this mean we stop using freedom all together? no. does it mean we surrender it for the good of those who are stumbled by it? yes.
if Christians would all apply these simple Scriptural principles, there would be a lot less petty fighting and contentions among the body of Christ.
one disclaimer should be mentioned at this point: if a person is attempting to set up their own convictions as law for others (which really means they are trying to set themselves up as god), we should contradict and break their convictions boldly. if they are contradicting the will of God through their man-made convictions, we should ignore them. Jesus often practiced this when the pharisees attempted to thwart the work and will of God by their extra-biblical convictions. Jesus' response was to boldly contradict them and continue anyway with the work His Father was doing.
well, hope that was beneficial for someone out there. feel free to share your thoughts in the comments.