I know people who have raised them, and have also read of raising them.

They are supposedly pretty darn placid.
I think the fact that dedicated owners spend time each day with the animals is a factor.
There is a woman here in Ala. who raises Texas longhorn champions, the "champion" part is for the length of their horns.
Pics in the article show her standing next to several of her cattle, petting them.
And i know cattle men around here who spend time with their animals, have no problem with bulls.
The bulls are often penned/pastured apart simply to prevent unwanted breeding.

So, again, proximity and care may be a huge factor.

or, better yet, getting calves and raising them? It seems like he's starting with the difficult part first?

These animals are for meat.

But you asked the same question I asked him: why not cows???? Maybe start off with some breeding stock?

not the best for meat but OK and obviously do well in colder climates. they need to be steered (castrated). bulls are always bulls, just like a stallion is always a stallion. not to be trusted no matter how tame.