The non-LDS kids who come to BYU understand that they must at least respect the LDS Church. They aren't required to join the Church or be kicked out. They are only required to meet with an ecclesiastical leader of their choosing, obtain her/his endorsement, and live the Honor Code. If, however, they choose to similarly go public with anti Church activities, they would receive the exact same treatment as an LDS student leaving the Church. They would have broken the Honor Code they promised to uphold and would face the consequences that are associated with that decision.