Here's the part I especially like:
"The LXX never uses [koinos] as expressed her in Acts 10:15 and 11:9…The single usage of [koinos] in Jewish religious/historical literature of pre-NT times occurs in the apocryphal 4 Macc 7:6, where it conveys the meaning of cultic profanation."….It is recognition of the fact that the NT incorporates and reflects this exclusive Jewish sense of [koinos] that illuminates why Peter should argue with his Lord over whether he should eat the 'clean' creature. In his mind, the 'clean' creatures in the sheet of the vision had now been rendered 'common' through being defiled by the presence of the 'unclean.' As F.F. Bruce points out, in a statement noted earlier, Peter 'was scandalized by the unholy mixture of clean animals with unclean.'…Furthermore…the voice itself never mentioned 'unclean.' It [reprimanded] Peter for declaring creatures to be 'common.' He was never directed to consume the 'unclean' creature, but rather immediately to desist from describing as 'common' the creatures that God had declared 'cleansed.'"