There's a little fundamentalist congregation in my neighborhood whose website bids all welcome if they subscribe to a very long list of doctrinal preconditions. There are a lot of fundamentalist and right wing Christians who are subjecting Anders Breivik's long screed to doctrinal acid tests in order to prove that he's not really a Christian, and therefore his violence does not contaminate them.
As far as I'm concerned, anyone who calls themselves a Christian is one. I will let The Chairman of the Board decide for Himself who really is or is not a member. Anders Breivik calls himself a Christian, so he is one. I can't imagine the same Christ that I pray to in any way blessing what he did, but, he's still a member, a brother, a part of the mystical Body of Christ on earth, as far as I'm concerned. He's an evil member, but a member. He's a monster, but he's ours.
A Christian, as far as I'm concerned, is anyone who says they follow Christ whether or not they believe correctly or incorrectly; whether or not they do great good or great evil.
Our responsibility as Christians is not to distance ourselves from him or his evil, but to fight that evil, to resist it, to do all in our power to stop it, to undo the harm it has done, and to bear witness against it.
God Will Be Mocked.
The people who truly mock God are not the people who don't conform to whatever template we make for them. The people who mock God are those who kill and harm, or who advocate harm in any form, to those created in His image. People like Anders Breivik and people who have similar sympathies spit in God's face just as surely as did the soldiers on that first Good Friday.