The Failure of "Tradition" Justification

Those who use try to use “tradition” or “custom” to justify and action (or non-action) should not be allowed to get away with doing so because that idea can support literally anything. In Chapter 2 of the book Guns, Germs and Steel by Jared Diamond there is a section talking about a South Pacific population called the Maori and their overtaking a neighboring population called the Moriori. From the book: 

“A Moriori survivor recalled, '[The Maori] commenced to kill us like sheep...[We] were terrified, fled to the bush, concealed ourselves in holes underground, and in any place to escape our enemies. It was of no avail; we were discovered and killed—men, women, and children indiscriminately.' A Maori conqueror explained, 'We took possession...in accordance with our customs and we caught all the people. Not one escaped. Some ran away from us, these were killed, and others were killed—but what of that? It was in accordance with our custom.'”

For those who use the "tradition" justification for any action have offered the worst kind of rationalization. Without something considerably more substantial to support a position, the use of "custom" should be rejected.