What sparked up the latest brouhaha was the separating of children from their parents in detention at the US border crossing. Such a terrible thing to be empathically concerned about. Good grief
That isn't really what ends up being debated, it's certainly not the focus of the topic as it's started - it's begun as a way for people to make accusations and throw mud, adding a few claims of racism and genocide along the way. What better cover than pretending you're concerned about "the children".
It somehow became a fight between the right and the left political spectrum within the United States why ?
Well, we do know ... it's because it's started precisely to be a fight between the different political sides.
It should have been evaluated as a social humanitarian concern or debate.
If it had been framed / started with that intent, the discussion would be different. Really, if it was "WE have been separating kids at the border for the longest time regardless of who is in the WhiteHouse. Is it right? Is it necessary? Should we still do it?
That way the discussion can be about the thing, not whether it is only a policy of a certain president or not.
But when it's started as "Trump started this, is solely responsible for it and is a monster for doing this and so are all the people who don't object to it" then the natural response is for people to point out that the evidence is otherwise, that Obama did it more etc... and it becomes one side vs the other trying to cast blame and not really about the issue.
In fact, people are so determined to cast the blame that even when people present the reasons that their own guy used to justify it, they refuse to accept it because doing so would admit the new guy is justified in doing it too - how can you have a discussion when people refuse to even base it in reality of historical facts?
But of course the people starting topics like that are not doing it because they really have any concern about the people involved, they are solely focused on having an avenue to attack the current administration because they won't accept the outcome of the election.