His lawyer says that he doesn't understand Breivik's motives, but they're spelled out in the same article. Alien cultures are being imposed on European countries and a lot of people are unhappy about it; if they wanted to live under Sharia they'd move somewhere that had it. Personally I think that this will not be that last time something like that happens, but I expect more of it in the USA.
Killing people who are no physical threat to you is automatically terrorism, even if I agree with your general grievance. Organizing politically to get a government which represents your views is more difficult, but that way you won't drive away people who might agree with you. Recent events in Holland have shown the lengths the leftist multicultis will go to to suppress ideas they don't like, but the truth will occasionally out as long as you keep things civilized. That is after all what we want in our civilization, not to stoop to the terrorists' level of killing people as your main argument.