All anarchists are opposed to nationalism.
Nationalism is an opportunistic way to prey on people's prejudices and stereotypes and fuse them into a social movement to achieve some goal. Typical of nationalists is hostility toward internationalism. Internationalism maintains that all workers have common interests, and it is the nation that pits workers against each other and brings war and strife to humanity. Sometimes nationalists use Christianity as a religion to rally around in order to be Populist. Other times they use paganism to seem radical and different.