This quote suggests that the most common and widespread mistakes or misconceptions in society require the highest level of selfless virtue to support or tolerate them. In simpler terms, it takes a lot of patience, understanding, and selflessness to deal with widely accepted but erroneous beliefs or practices.

The "broadest and most prevalent error" could refer to any widely accepted but flawed belief or practice. These could range from societal norms, cultural practices, or even popular misconceptions. The "most disinterested virtue" refers to a kind of virtue that is selfless and unbiased, a virtue that does not seek personal gain but is purely for the sake of doing what is right.

Applying this to today’s world, we could think of various prevalent errors such as racism, sexism, or even climate change denial. These are broad, widespread issues that are erroneous in nature but are still prevalent in many societies. Sustaining or tolerating these errors requires a high level of disinterested virtue. It requires individuals to go against the tide, to stand up for what is right even if it is unpopular or inconvenient.

In terms of personal development, this quote could be a call to cultivate such disinterested virtue within ourselves. It encourages us to develop the courage and moral strength to stand against prevalent errors, to question popular beliefs, and to seek truth even if it goes against the grain. It’s about developing the ability to do what’s right, even when it’s difficult, unpopular, or personally disadvantageous.