The last argument will make every other meaningless.
Congratulations.
Crime has dropped every single year in my country for the past 25 years, we do have open borders. I'd say that has nothing to do with criminal activities.
You are blessed. We are not so much blessed here. We have open borders too. The criminality has risen since 1995 a lot, and since 2015 like Bitcoin. And that was not surprise for me.
We have interpol, we have "face-recognition" cameras amongst things we don't know about.
Face-recognition cameras all around is one result of the borders without control. And face-recognition is far more Orwellian than the border control on the borders of the country. At least it is for me.
Having borders everywhere would just complicate things, think about international transport and trade.
The border control is not needed "everywhere". The Border control is necessary only on the borders. And like I previously mentioned, if there is no border control on the borders, then the border control will be "everywhere", on schools, restaurants, roads and so on.
International transport and trade is not disturbed by the border control. The transport and trade is done all the day around, all the time over, already. Over the controlled borders, with no problem.
I do agree we must have some lines drawn, as there are places/people who can't integrate and whose cultural behaviour will never meet the standards of others. People are just different. But in EU the Shengen area has made things much easier, not vice versa and like said, I don't know anything about risen criminal activity, please do educate me if you have any information on that.
When the first lines are drawn again on the border, there will be far less cultural behavior like rape, murder, robbery, pedophilia, terrorism and violence inside the controlled borders.
In addition. The prerequisite for functional schengen area would be the border control on the outer borders of schengen, which exists in legally but not practically.