Rav Linzer’s daf yomi shiur is available online for the whole world to hear.
A conversion, once the ger leaves the mikvah, is done. You cannot retroactively annul someone’s Jewishness. Lifestyle doesn’t make them Jews; they fact that they underwent the procedure of conversion makes them Jews.
How is a more liberal bet midrash akin to a church? What demigods or statues are they worshipping in Yeshivat Hadar?