Is my violation of the Hadith: "None of you [truly] believes until he loves for his brother what he loves for himself" realized if I strive to marry off my brother, who belongs to the Tablighi Jama'at—which I do not approve of for myself—to one of my friends?

The Tablighi Jamaat, like other da'wah groups, has its efforts and fruits, but also some observations against it. If the brother is pleasing in his religiosity and character, a follower of the Sunnah, and cautious of innovation, then there is no harm in marrying him to your friend. However, if he insists on an innovation or travels extensively and it is feared that he will continue to do so after marriage, then do not intercede for him, and he should marry someone who is in a similar state as himself.