You will notice that God established marriage before the fall of man, which was before Adam and Eve sinned. The fact that we tarnish marriage through divorce, infidelity, affairs, or co-habitation does not reduce the importance that God places upon His original design. Nor does our tendency to not do marriage well provide us with just cause for the redefinition of it. Same-sex marriage included.
Now, if you don’t’ want to submit to the teaching of the Bible, that is your choice and no one is forcing you to. You are free to choose whatever lifestyle or religion you choose. But if you choose to identify with Christianity, you do NOT have the freedom to pick and choose which Scriptural commands to obey. While none of us keeps the commands of God perfectlly, we should, however, at least have the desire to keep them and should be striving towards obedience to them. All of them.
On the other hand, if you do not want to submit to the clear demands of Scripture, then why claim to be a Christian? Feel free to call yourself whatever you want, but it will not be Christianity.
Take for example the Episcopalian church. This organization has embraced homosexuality as a God-approved lifestyle, ordains gay ministers, and endorses same sex-marriages as a redefinition of the family. All this is defiance to the Bible.