In White Fang, what do theives learn from White Fang?

The thieves learn that their presence will not be tolerated.... they learn humility.

From the text:

But White Fang soon learned to differentiate between thieves and honest men, to appraise the true value of step and carriage. The man who travelled, loud-stepping, the direct line to the cabin door, he let alone—though he watched him vigilantly until the door opened and he received the endorsement of the master. But the man who went softly, by circuitous ways, peering with caution, seeking after secrecy—that was the man who received no suspension of judgment from White Fang, and who went away abruptly, hurriedly, and without dignity.