J.A. writes in his apology (from English PDF version) thus:
"The “warmth and friendliness”, that “do exist within the Group”, are what we wish to share with every person. But a certain common ground is necessary for that. For us, the terms, “brother” and “sister”, are not just religious clichés,..."
This lapsus linguae shows clearly, with whom their warmth and friendliness is limited: with brothers and sisters in Christ. With their community. Take it as you want.
However, Jesus didn't say, that we need at all 'a certain common ground' for showing warmth and friendliness. Jesus expressed in Matthew 5:39-47 rather something quite opposite:
39But I tell you, do not resist an evil person. If anyone slaps you on the right cheek, turn to them the other cheek also.
40And if anyone wants to sue you and take your shirt, hand over your coat as well.
41If anyone forces you to go one mile, go with them two miles.
42Give to the one who asks you, and do not turn away from the one who wants to borrow from you.
43“You have heard that it was said, ‘Love your neighbor and hate your enemy.’
44But I tell you, love your enemies and pray for those who persecute you,
45that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.
46If you love those who love you, what reward will you get? Are not even the tax collectors doing that?
47And if you greet only your own people, what are you doing more than others? Do not even pagans do that?
Actually, for me it seems to be impossible to love enemy. It has become also a real challenge for me to love those, whose love to Jesus is outside the community experienced mostly with their overthrowing the tables of the moneychangers, and the seats of them that sell doves. It is hard for me to love community so, that also community and everybody would experience it in the same way as described in Mt 5:38-47. And this is truth, that for man it is impossible. But this is possible for God. Therefrom differs God's love from world, too.
For this impossible love is God calling us.
Really, incredible. Wonderful.
It is difficult to love enemy. And not because enemy doesn't let to love himself. Vice versa, this is the best opportunity to practice the love described in Mt 5. It is difficult to love enemy, because of our own attitude, our own lack of mercy.
It is hard to acquire this attitude, which has the effect described in Mt 5, according to which the consequences of love are experienced in the way described Mt 5. This good attitude has the results described in Mt 5, which does not forget first to pray for those, who persecute us (Mt 5:44), which is perceived to EVERYBODY as we can read out from Mt 5. And thereafter we may try also 'to say the truth' and 'assess' them, if we need it necessarily. If it is necessary at all, because to assess your enemy is nothing special we can identify with love. It is quite easy 'to assess' your enemy and 'to say the truth' to them. It gets easy. This is the first reaction, that comes from human behaviour. And if you think, that unbelievers 'don't see the truth', then it is very naive. I've experienced several times, how carefully unbelievers assess Christians' behaviour. They notice very well, when we transgress the moral principles.
We know, how much unjustice there is in the world and in ourselves. It is no news. The good news is, that God has shown us the love, which reached us before any of us was worthy to.
Let's do something special: keep trying to exercise together the impossible love? I think it is good to start with them, whom it seems impossible to love, with whom we don't have any 'common ground'. Because it is said:
"And if you greet only your brothers, what are you doing more than others? Do not even pagans do that?" (Mt 5:47)