Justify, Justify, Come On Up and Justify!

Sooner or later every openly gay Christian hears an argument that goes something like this:

You offer no Scriptural evidence to justify same-sex relationships in the eyes of God.

Or perhaps:

Unless you show that same-sex relationships are acceptable to God, they are wrong.

Now, that's a dangerous style of argument for many reasons. First of all, it implies that we can justify ourselves before God.