Just enough so that, by the time I finish the cereal, there's only a little milk left.

Edit: The way I do it is to have a layer of granola on the bottom, then a layer of whatever floaty cereal on top. When I fill it with milk, it's a little bit below the top layer so that it's just a little less than what would make it float. That usually gives me the perfect ratio.

One Day - Matisyahu
https://www.youtube.com/watch?v=WRmBChQjZPs

The vast majority of Christian religions don't have anything against modern medicine.

The fact that a girl is now dead because of these extremists is heartbreaking.

There's a popular parable/joke that's often told among those who are religious about a devout man in a flood who rejects multiple rescuers while saying, "God will save me." He then eventually drowns and complains to God. God then responds with something like, "What do you mean?! I sent 2 boats and a helicopter!" https://en.wikipedia.org/wiki/Parable_of_the_drowning_man

For Christianity in general, there's a saying that we should first do everything we can and then leave the rest in God's hands. There's a whole section dedicated to this with the most relevant part:

What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him? (James 2:14)

Any Christian religion that chooses to ignore modern advances in medicine (be that vaccines, insulin, or whatever) shows that they're ignoring a fairly obvious lesson that the rest of Christianity has already learned.

Honestly that sentiment depends on where you are in the world.
There are some parts of the world where it's very common to discuss religion, there are other parts where it's taboo, like you say, it just depends on where you live in the world.
The cool thing is that the internet has brought us all together. However, I find it common that we also assume that others share the same "common sense" that we do, even when "common sense" itself can vary widely from one community to the next.