Christians do the same. If we are to take the Bible at all seriously, at least acknowledge every part of it. Christians are VERY good at ignoring the parts they don't want, and say the Bible shouldn't be read that way, picking and choosing parts- basically making it impossible for anyone against the bible to back up their opinions with evidence. It's a pain in the butt, and why is it ok when Christians do it to back up their points? I can't see what's wrong with picking and choosing parts to support your arguments. They are in the bible, it's written right there, so why aren't we allowed to use it?
They're stories that some people put faith in having actually happened.
So basically it's what ever you want. But some people will craft their own religious beliefs to tell you you are wrong if you do.
Personally I worship the plate of spaghetti that Zeus ate at the beginning of the Universe.
For instance, let's take Christianity: the Bible has some bad parts, but if one identifies as a Christian, that means he believes in the Bible, not just the parts that he wants to believe in. One must accept what is written as the word in a religion. The part about slavery is no less valid than the part about honesty, for they are both written.
If you are not debating religion, the bible has no place for the argument. For example, if you are debating gay marriage and they say "The bible says..." That is incorrect. Also, the Bible was made by man, not God. If you are going to bring the bible into an argument, you must also relate it to the outside world today.