Here are some other ways to "stumble your brother": Buying a CD and listening to it in your home or on headphones, so no one else has to listen to it. (Anything other than a Kingdumb CD.) Watching a slightly dirty movie in your own home. Buying Christmas candy for personal consumption, even if it is marked down 50% after Christmas. Having a fuzzy dice decoration in your car. Reading a worldly book on your computer or at home. Drinking one beer at a bar (not enough to get drunk by any means). Going inside a disco or nightclub. Getting Internet, especially if you are going to look at those horrible educational sites. Having nice things (that would be materialism, and would stumble others into not donating to the Kingdumb work). Having things that look nice (also gives the appearance of materialism).
I guess they haven't heard of the latest way to stumble others: Independent Thinking. That idea is not new--even though there are groups of people emerging that are trying to make that become widespread (it was Aristotle's original idea, not some modern group's). Independent thinking means you are responsible for any action you volitionally do. You are not responsible for what anyone else thinks: If you go to that disco or bar, others are responsible if they choose to likewise go since they have the choice to not go. If people are independent thinkers, they will do things only because of the consequences of those actions and not because of someone else doing it.
The "stumbling" is one more way to keep the flock in "bicameral" mode (bicameral mode is where someone or something tells you what to think or do, and you merely follow rather than self-leading). People in bicameral mode are highly susceptible to being stumbled, such as by apostate Web sites or someone's actions that are questionable. Independent thinkers, on the other hand, will not be swayed by such material or actions. So what if someone in the Kingdumb Hell is taking horse! It's not my brain and liver that will be ruined!