So, effectively your objective criteria is the Bible because you have no way of knowing if the Christian God really does exist outside of your own mind, and even if you did you would have no way of knowing what his judgements about right and wrong were without the Bible.
I've already explained some of the evidence I take to indicate the existence of God (the fact that all humans seek meaning and objective morality, the testimony of witnesses). Some of this is in the bible, some is not. The bible as a whole effectively provides an explanation which, together with the evidence available suggests that the true God is the Christian God. Ultimate truth about the character of the Christian God can only be known from the bible but some indicators of his character exist in things that are observed in ourselves and the universe.
But yes, the final authority on God's 'judgements about right and wrong' come from the bible.
Now Bible interpretations are subjective judgement calls, ruled by what your own conscience tells you is right and wrong, (unless you are a Biblical literalist). That is why people don't execute disobedient children or adulterers anymore. Its why some Christians are ordaining gay bishops while others are picketing funerals with signs saying God Hates Fags.
Not really true. Some Christians would take a different view of the importance of the bible as a source of information about God and his judgements. In such a case, the difference is not in interpretation but in the place of the bible as a whole.
In addition, some people might call themselves Christians but make no attempt to regulate their behaviour by what is written in the bible at all.
Some might use the bible but just fail to live up to what it commands - even though they agree with it.
As a result, it is not correct to point to differences in opinion and behaviour about moral issues and say that it is all about 'interpretations'. This would be akin to saying that because some people disagree that the process of evolution is responsible for the diverse living species that it is all about 'subjective interpretations' and the truth cannot be known. The data is there, external to our minds and therefore the possibility for a 'true' understanding exists.
Because the bible exists as an objective document (external to both your mind and my mind) means that we can at least have a discussion about its content. It is not a forgone conclusion that we will come to a different explanation and its 'true' meaning may be discoverable. The fact that people might disagree does not mean that a true meaning doesn't exist.
With the conscience, this is not the case. You can tell me what your conscience tells you and I can tell you about mine and we may even agree - but there is no case for 'true' or 'untrue' that can be made. You could lie to me about your conscience and I would have no means to correct you. For this reason, if conscience is your only guide, then you have no argument to object when someone behaves in a way that you don't like if they were also following their conscience. That's the reality you need to face as an atheist - no meaningful judgements about right and wrong at all!
Face it, sparky, the Bible is only objective to you in the basic sense that it exists outside you.
And that is a fundamental and manifest difference to relying on 'conscience' alone.
Using it as a moral guide involves just as much subjectivity as deciding your morals without it.
Not true at all. If something exists only in my mind, no-one else has access to it and even I cannot really be sure that is anything more than my last meal speaking. With the bible, that is not the case, we may disagree about interpretation, but the data is still there for reference. In the case of the bible, the material spans a long period, contains a variety of different types of literature, comes from a variety of authors and is extensive in length. As a result, the material available for cross-checking interpretations is plentiful. As a result, the possibilities of determining a 'true' meaning are far greater than for a purely subjective source which, as I have said, is changeable, influencable and unclear.
Cheers,
sparky