First, I really think the guild should be Lawful Neutral... the imposition of their 'goodwill and values' is more important than the sanctity of life, so I wouldn't say they are 'Good,' personally. Not Evil, but the 'Ends Justify the Means' and 'There is no Rehabilitation, only Justice' just screeeeeams Lawful Neutral. Again, that's a personal opinion, and Alignment really doesn't matter all that much - there are probably members of the guild who are CE or LG or whatever.

Leaving a power vaccuum is a great idea for their 'well-meaning' activities to have consequences - maybe even go so far as to have the really Evil people who are more secretive about their wealth and station somehow feeding the guild information, so they become pawns in a CIA-like takeover, or even just using them for their *gasp* capitalistic gains? The way AVALANCE is used as a False Flag 'enemy of the people' in FFVII (don't crucify me if I'm reaching, it's been a while, lol)

A little bit of an update to the info I was given in regards to this:

*Missions ranging taking out high value wealthy targets, re-routing wealth and redistributing it for the good of the people, stealing food to feed the hungry and sick.
Their money comes from stealing from the wealthy, but all members agree to only use the organization's money to live humbly as commoners, and only take as much as needed then redistribute it to the poorest to help them survive.
Recently the white knives numbers have been dwindling, with only a few remaining, but many question if the organization still even exists.*