From what I know about some of those groups, they think that the entire reason muslims are in Europe is because of Jews in the first place. Every single mention of Islam conquering Europe always ends up with speak of the Jew and his desire to destroy Europe and the "white" race. Many of these nationalist groups would take out Jews along with muslims because they see Jews as an eternal enemy. The arab population is 4%, Craig Winn demonstrated that in a dedicated and ruthless minority with such a strong ideology like Islam only 3% is required to overthrow the political and social order.
Also, this statistic is deceiving because the percentage of 18-40 year old muslims who are willing to fight compared to European men willing to fight is higher, plus if no demographic changes at all happened and birth rates remain the same, the muslim population will double by the next generation. The problem is that Islam tells their followers to lay in wait, in order to build up their population to eventually conquer and destroy. They tell everyone how peaceful they are and how they just want to be European, but you can see the entire time that they are not actually European but still strongly identify themselves as muslim. Just look at the polls, most of the British muslims supported the 7/7 attack. They will lay in wait, and their target prey of Europe is perfect for their strategy. They pretend to be peaceful while they amass numbers in Europe, and then once the time is right to strike they will do so, viciously, and the Europeans will be completely caught off guard.
The most racialist, nationalist, right-wing youth of Europe who are willing to fight are NOT against the muslims, they are more against the Jews. Just go into any white nationalist website and see what they talk about the most. These people study Jews as their life profession, trying to delegitimize our connection to Israel, etc, while they are largely ignorant of the true nature of Islam and its followers. I posted an article I wrote on a white nationalist board, telling them that Jews were not their problem and that in fact it was Islam. The moderators did NOT post my article, because it challenges the movement's dogma and threatens the control they have over their followers. Indeed, all the most right wing groups in Europe are similar in their ideology concerning Jews and islam, the Jews are the bad guys, not the muslims.