The brain is only a skein of neural excitations. To analyze the motives of an action, one must look at the level of mental representations. It is they who are active, and capable of confronting others, antagonists. However, the most active of our representations are those which we call identity. They have a celebrity that stifles others, even more judicious in the context, because this judgment is outside of identity. You can thus see our acting representations as a bunch of aristocrats who self-justify their behavior, no matter the consequences. They support one another, and only a cat among the pigeons can break their union!
To make your question fair it would have to be reversed: it is rather our actions that are now seeking excuses in the brain. Rather than endorsing responsibility for behavior themselves, they tend to say today: « It is the brain that has chosen it ». And soon they will put our genes in the box of the accused. Very clever. Who will want to put an unfortunate piece of DNA in prison?