I gave it a couple of tries Henryk, but think I must put this on ice for some time. It is such a controversial topic.
If I was to be entirely honest about what I thought about a lot of these things I would risk running the errand for racists and xenophobes. It is a delicate balance almost impossibe to find. If you sugar coat reality too much, they will accuse you of hiding the truth or being naive.
If you speak too plainly, they will likely quote you in their propaganda. Either way you lose.
I don't think we realistically will ever end up with open borders, because most sane people don't want that. Hence I probably don't need to advocate against it either. I think what triggered me to write originally is the notion that we in the West are somehow racist because we don't favor open borders. Secondly because I am a leftist and hate seeing the left gather behind this as some kind of key political agenda.
In the end I think I would rather spend my energy writing against racism, than writing against open borders. The former is a real problem, while the latter is just a theoretical construct that will never come true.