A number of fine posts have appeared addressing the question of whether being a Lutheran matters any longer or not. The answers, and the clarification sought by Pastor Wilken, are excellent. Still, the question is not fully addressed until one understands that the question is actually, "Does truth matter any longer?", or "Does it really matter if one is a Christian any longer?".
One senses a reluctance in certain quarters to identify the Lutheran confession with truth, or the Lutheran faith with the Christian faith. But what else is it? If our confession is not the truth, why do we stand on it? As one wise (and inspired) man once wrote, ". . . what partnership have righteousness and lawlessness, or what fellowship has light with darkness? Or what harmony has Christ with Belial, or what has a believer in common with an unbeliever? Or what agreement has the temple of God with idols?" And, if there is a difference between the Lutheran faith and the Christian faith, that the two may be distinguished as readily as many seem to do, why do we cling to that which is not fully or truly Christian?
No, Lutheran is Christian, and Christian is Lutheran, whether one bears the label or not. To the degree that one's faith departs from true Lutheranism, ones faith also departs from the Christian faith. Clever and sophistic evasions of this confession abound, but the truth of the matter is that if we cannot make that confession, we ought not to call ourselves Lutheran, and ought not to seek to cling to the Lutheran faith because the failure to be able to clearly confess this truth is to manifest that one is not really Lutheran, or one does not believe themselves and their faith to be fully and honestly Christian.
Now, this is not necessarily the approach to discussing the faith that I would recommend for outreach, but it surely a reasonable approach to teaching the faith to those who also call themselves "Lutheran". People need to learn first about the faith before they will be ready to confront the reality of the counterfeits of the faith and the distortions of it that abound in the world. But, if those who are charged with teaching the faith cannot readily confess the truth of what they teach, and say clearly that their faith IS the Christian faith and those confessions that disagree have disagreed with historic Christianity, who will? And, what does their refusal to say so say about them?
Are there Christians outside of what is called "The Lutheran Church"? I believe so, and surely hope so, but they hold a Lutheran confession to the extent that their confession is Christian. I will also admit that everyone who calls themselves a Lutheran may not truly be a Lutheran. That is sad, but it is also one of the logical conclusions of this post. Those believers who do not call themselves Lutheran may hate the name, "Lutheran", but if they believe in Jesus Christ, and trust in His grace and hope for the blessings of the Gospel - like forgiveness of sins, resurrection of the body, and life everlasting, all by grace - then they hold to the Lutheran, and therefore the Christian, faith.
There is no real distinction between Christian and Lutheran, except, perhaps, the labels one chooses to apply to oneself.