By ignoring that aspect so long as the fundamentals of Salvation are assured. If this belief you pointed to aides a ‘faither’ in their walk with God, leave them be, to be transformed by the Spirit of Truth.
ec·u·me·nism (ky-m-nzm, -ky-)
n.
1. A movement promoting unity among Christian churches or denominations.
2. A movement promoting worldwide unity among religions through greater cooperation and improved understanding.
Unless ecumenism is aimed at greater understanding of and greater obedience to God, maybe we shouldn’t have it. And labelling the pursuit of holiness “tripe” hardly advances it anyway.