There are some Christians who don't need to knock on doors. Their conduct in daily life is an ad for Christ. Going to church, boasting on scriptural knowledge, etc. is not that impressive. I've been fortunate enough to several such people. Of course, they would prob. be outstanding in any religion.
The Amish who forgave the murderer of young girls at a school had everyone amazed. The perp's wife was included in all of the services.
Quakers impress me. The Roman Catholic Church impresses me negatively but some aspects of the church, such as Catholic Charities, are very moving. k
Pagels reported that Christians were charged with crimes against humanity. Only baptized members could be present for the Eucharist. Calling each other "brother" and "sister" combined with eating "body and blood," one can see why they were so reviled. I am not certain when unbaptized members were allowed to attend Eucharist. This very negative feeling that Christians broke all human bonds changed when Christians stayed behind in plagues and ministered to all, not only Christians. Slavery was rampant. I believe I heard about 75% of the populace were slaves. The value of each individual in Church, the mixing of high class and slaves at agape meals convinced people something unusual was at work.
Words are cheap. Conduct is much harder.