n0mesorah,
“But I should not be concerned that others are not thinking wrong. I answer amen to someone’s bracha even if I didn’t debate their belief in anything. My thoughts matter to me. Someone else’s doesn’t.”
If 9 people are waiting in shul and a man walks in with tallis and tefillin, we go ahead with yishtabach and kaddish, even if we don’t know him. We answer amen to his brachos. We may even give him an aliyah. This doesn’t really contradict what AviraDeArah is arguing. We give people who profess and act as frum Jews a chezkas kashrus by default. If we later learn that the man is a kofer, we no longer give the chezkas kashrus.
“Show one source that I should get involved in your yiras shamayim.”
What if a kehilla were considering this man to be their mora deasra?