Peace and division
Of course the same Jesus who said that about the devil's kingdom if it were actually fighting against itself also said, "Don't think I came to bring peace. I came to bring division - in one house father against son and against father, mother against daughter and daughter against mother, mother-in-law against daughter-in-law and daughter-in-law against mother-in-law."
The unity that God looks for is not established by us. It comes from above (Psalm 133), like every perfect and good gift (James 4). And it doesn't happen until we stop trying to enforce our own order and unity and permit ourselves to be subjected to the order and unity of the truth. That's the long way around, but it's the only way around. Like Jesus hanging stark naked on the cross, we'll look like public spectacles while we wait for it to be done right by our God. Tough indeed to go there. But that is the only path to resurrection. And we can't explain it any more than Jesus could win any arguments with his tormentors there on the cross, except in the conscience of one thief.
Afterwords, as the earth quaked and and the sky grew dark, as the graves were opened, as the veil in the temple was torn - now things were different. In his death according to God's will, Jesus won some arguments he wasn't going to win otherwise, including the one that really matters - against death.
We're not going to get there through our zeal and determination, or by applying anybody's rules, including Bible rules. God has to take us to school to become like him. There are some great classes there that nobody signs up for. It has to be court-ordered, which is how we find out that there is a Court in heaven that rules (Daniel 4).
So Jesus says, for instance, not to resist him who is evil, but he didn't forget the proverb that reads that those that keep the law strive against the wicked. The scribes and Pharisees felt pretty resisted, didn't they?
What is this all about then? Well, for sure it means at least that our response is never to be to what someone says or does, but to how God wants to handle it. We're not to resist the wicked but to stop being wicked ourselves, instead listening to the God of truth and following him in the situation. That way those that hate us can help us to learn obedience by giving us some practice.
Well, how does that look? Sometimes God wants to let himself be pushed around and be weak, so to follow him means to go there with him. Sometimes God wants to push back, so then we need to go there too. And all the time, we need to learn from what God does with us how to deal with others. It's fine to be tough with others if we're up for God being tough with us when we act the same way - and sometimes that's just how it has to be - but if that whoopass isn't what we prescribe for ourselves then how can we prescribe it for another?