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This cannot be said often enough!!!
I soooooooooo wish every Christian would remember this. We all need to show grace to our Brothers and Sisters in Christ on matters that aren't Salvation issues. This includes Copt, Orthodox, Catholic, Lutheran, Presbyterian, Anglican, Church of England, Episcopalian, Methodist, Mennonite, Moravian, Anabaptist, Baptist, Non-denominational, Charismatic, Pentacostal, Church of God, Church of Christ, Nazarene, Quaker, Messianic, etc., Christians, whether conservative or liberal. It's actually a lot easier for individual believers to put this into practice than it is for clergy, churches, and denominations. When Christian A lives next door to Christian B, where each of them goes to church loses a lot of importance once they find out they each have John 3:16 right and will be going to Heaven
Differences in respectful conversation iron sharpens iron. Every denomination and church on the planet has something wrong with it, whether it's doctrine, theology, practice, and/or something else, because all are led and attended by sinful human beings. Some errors are more easily recognized than others, even by lay Christians, and many arise from different conclusions and interpretations from sincere and earnest study of Scripture.
Once hard persecution against Christians starts in earnest in the West, the persecutors won't care which denomination, and Christians won't be particular about denomination or non-Salvation issues when getting the opportunity to worship at an underground church or secret home church. I had no issue going to an underground church that wasn't Lutheran and participating in Holy Communion. Here, where there are choices and the luxury of being particular, that church would not have Communed me, and I wouldn't gone to that church. Persecution makes the Church stronger, in part because it forces Christians to focus on what is important and stand together on those things.
Even now in the US, if there is no church of the preferred denomination or specific set of beliefs, Christians are forced to choose from reasonably available options, not go to any church, start their own church, or have family worship. As more churches shut down and/or doctrine, theology, and/or practices change, more of these kinds of decisions will have to be made.
Although forced busing to facilitate school integration wasn't a persecution issue, what happened in the 1960s and 70s here illustrated what people will do when faced with an unpalatable enough choice. When the government was going to bus kids away from their neighborhood schools, the Catholic schools here opened their doors to non-Catholic kids (with a recommendation from a Catholic), but before that, the Catholic schools were all Catholic-only, and wouldn't have ever considered a Protestant kid, even with recommendation(s) from Catholics. And Protestants went to those Catholic schools, whereas before the government edicts, they never would have even considered doing so. The one concession the Catholic schools made for the Protestants, at least the ones near where I lived, was waive religion classes and Chapel requirements for Protestant kids, whose parents didn't want their children to go. The only other choices were non-religious private schools, other religious private schools (very, very few), and homeschooling. Pre-internet, so very little support and very few readily-available resources to parents. I don't know what happened elsewhere, just here.
There won't be denominations in Heaven. Just Sons and Daughters of The King, who went to all sorts of churches, good and bad.