Tiandu Emperor once said that as long as one can pass the trials, any method can be used. It seems that his words are meant to convey a principle to these geniuses - when facing demonic beasts that are not of their own clan, they must use whatever means necessary, and there is no method that can't be used against enemies.
As long as they can win and defeat their enemies, anything goes.
Upon careful consideration, Yang Chen agreed.
When the Demon Beast Clan faced humans in the past, did they reason with humans? They must have used all kinds of conspiracies and underhand tactics. As they were not of the same clan, there was no need to talk about any Dao intent.
It's the same when humans encounter demonic beasts. What can you reason with them? Any means are acceptable as long as they can win.