Those oaths are basically a way of taking the name of God in vain, if you use His name, or putting yourself under someone else's authority, which is worse.
The word God is never used in lodge. Due to the fact the Freemasonry is not, or a replacement for, religion they use a generic term so if a prayer is said each mason is saying a prayer to his god, whether he be christian, muslim, jew or whatever.
Now the use of a generic term is Freemasonry's way of saying you believe in who you want to believe in, just be true to that faith. This may be wrong in some peoples eyes, and you can twist it, not saying you as you personally, to make it seem they are prayer to some weirdo make believe god, but each mason knows who he is praying to. A Christian Mason, as far as he is concerned, is praying to the same God as you.
A Christian belongs to Jesus Christ. When he takes an oath, he basicaly commits himself to another person or institution and puts his allegiance before Christ. That's why a Christian should never take oaths.
Does the President, a doctor, a lawyer, a court judge, police officer and many more not swear an oath.
To serve and protect at all that?
As example in England
The Head of State is the Supreme Governor of the Church of England and “Defender of the Faith”. The Coronation Oath sworn by the new Monarch is profoundly Christian.
The Church of England and the Church of Scotland are also ‘by law established’.
Christian oaths are taken by MPs, others in public life and by witnesses in a Court.