Softwords,
1. I disagree with your assessment of the majority of the DL community.
2. On the contrary, the Gemara requires a man to teach his son a trade. In our thime this means secular subjects. Moroever, Rabbenu Bechaye and the Gra said that a person cannot be considered wise if he does not possess seven fields of secular wisdom (among them math, astronomy and music). The Maharal’s talmid muvchak, Rabbi David Ganz, was an associate of Tycho Brahe. The Netziv closed the yeshiva because the Russian government wanted to gradually eliminate religious studies. In contrast, the Pressburg yeshiva had an arrangement by which talmidim were exempted from the draft as theological students in exchange for passing the external baccalaureate (something like an academic high school diploma) exams.
3. Peace does not mean not disagreeing or not giving mussar. On the contrary, “????? ?????” is next to “????? ???? ????”. If pointed debating is friction (and BTW, I heard from one of his talmidim that Rav Gustman said that in Grodno it was permitted to call one’s chevruta any name except “baal bayit”) than let their be friction. However, my experience is that Chareidim and DL have no problem davening in each other’s shuls. Some Chareidim will not eat by DL but from what I have heard from Chareidi rabbanim this is am haaratzut (see Mishna Berura 318:2 that b’diavad one may rely on opinions that one does not generally accept). Marriages are also rare but that is also true regarding Litvaks and Chassidim as well asAshkenazi and Sephardi chareidim (among DL this si not an issue at all). This has already been discussed on another thread.