What you call "tribalism", political scientists would call "coalition voting". You're describing the straightforward product of Duverger's Law as if it were some idiosyncrasy of human nature and not the design of our political system.
The word "conservative" doesn't help us much here either. Are black families more likely to attend church than urban white families? Yes. Are older black voters more likely to have strong traditionalist views on marriage and marriage equality? Yes. Are black voters likely to respond to appeals to defer to the authority of the police? Very much no.
No, coalition voting is when political parties promise to support some of each other's policies in order to seize and share power.
Tribalism isn't about policy and it's concrete effects at all. Here's a great Howard Stern interview about it. The gist is that Obama asked a bunch of NY folks whether they support Obama because he wants to stay the course in Iraq or because he's pro life? His supporters agree with him on both policies and are glad he chose Sarah Palin as his VP. (The one McCain supporter in NY was no better.)
Tribalism isn't about policy. It's about identity and it seems to be the primary driver of voting. Trump is incoherent, and insofar as he had any concrete policy goals he's backed away from them (e.g. the giant wall of ice). But he shows respect to Vaisya Americans [1] so they support him. I imagine that if I spoke to typical white Trump supporters they would probably be as incoherent as Obama voters in Stern's interview.
This is also why Modi had to go so heavy on Hindutva to get support. "Toilets First, Temples Later" will help far more people, but he needs to ensure strong support among tribalist voters too.
Or even to go with your example, ask why people who incorporate "black" or "non-racist righteous white person" into their identity care so much about blacks being killed by police, and so little about blacks being killed by black civilians? That's directly comparable to the level of attention rural/suburban whites give to terrorism vs murders by rural white civilians. The former is an attack on our tribe by outsiders, the latter isn't.
[1] I'm taking the term from this article. In the US we deny these concepts so strongly that we don't even have words to describe them; as a result Moldbug had to borrow Indian words when discussing it. http://unqualified-reservations.blogspot.com/2007/05/castes-...
Sorry, I'm not going to Moldbug for a refutation of the concept of coalition voting or the idea that America's two political parties are an expression of coalition voting. The notion that the Democratic and Republican parties are and have been coalitions is extremely mainstream. If you want to challenge it, find a non-fringe source who's making that argument clearly and directly, and I'll read it.
I made the argument clearly and directly in my comment. Coalition voting doesn't explain the behavior in the Stern videos.
I only referred to Moldbug for a description of one particular tribe (Trump's) - ignore that tribe if Moldbug causes you too much angst. I included other examples. Do you have any argument beyond highbrow dismissal and appeals to uncited authority?
The word "conservative" doesn't help us much here either. Are black families more likely to attend church than urban white families? Yes. Are older black voters more likely to have strong traditionalist views on marriage and marriage equality? Yes. Are black voters likely to respond to appeals to defer to the authority of the police? Very much no.