I'm afraid I don't buy that rationale. For anyone who does not love his brother whom he has seen, cannot love God whom he has not seen. John was talking about church relationships but surely the principle applies to husbands and wives. If anyone says 'I love God,' yet hates his brother, he is a liar. I don't know any of those people about whom the questioner writes, but I recognize the possibility that some may genuinely qualify as Christians who haven't grown in grace and knowledge the way they should have.
Christians differ from each other in terms of maturity and spiritual development.
Patience needs to be expressed toward those who are still on the upward climb. Some people fail to recognize the fact that religious activity doesn't cancel out the need for relationship improvement. Reading the Bible, saying prayers, attending church and being involved in church ministry are all admirable activities, but you can do all those things and have a horrible marriage if you don't make relationships a priority. If you are truly submitted to Christ, you will be submitted to each other and that includes both husband and wife. Christ-like people don't go to war over who has to submit.