It wasn't really anything novel, but that was quite a believable back story for Bete. He was taught from a little child that strength matters and the weak perish, then demonstrated the same thing in practice when his whole tribe was killed, unable to defend themselves. On a bit deeper level, he doesn't want to make friends because he's afraid of losing them. Maybe Bell annoys him because Bell might be stronger than he was at the same age or after the same time as an adventurer. Bete might only respect the strong, but at the same time he grew in a place where you wanted to be the strongest, so everyone else strong is automatically a rival.
I'm not at all bothered by how he treats the others at the Loki familia. He said what he wanted, but then he left, not further agitating the others. The Loki familia is one of the powerhouses. The people at the top didn't get to the top just by any birthright, so there would be all kinds of personalities.
I do hope the Amazon girls stays around to pester Bete. She's amusing.