No one can force you to read people charitably, giving them the benefit of the doubt when they are ambiguous or make statements that sound heterodox. Indeed, even if you want to read charitably, you may not find it easy, particularly if you are a person prone to perpetual suspicion. It may be a habit you have to cultivate by careful practice of extending grace to those you read, especially when you don't feel they deserve it.
If you choose to exercise charity, you can still note red flags - statements that raise some suspicion or doubt about the charitable assumptions you are giving the author. Reading people charitably is not the same thing as automatically accepting everything they say as correct, or being blind to their potential faults.
Charitable reading should lead to a response of speaking the truth in love. In other words, charitable reading can lead to charitable responses. Those responses can be critical responses, but they need not be caustic responses.
Christian duty demands charitable reading and responses, particularly when it comes to the brethren, and most of all when it comes to elders. This duty, however, has to be fulfilled in the heart, a place where no church discipline can fully penetrate.
When you are trying to read charitably and you come to a head-scratching comment from the author, ask yourself: how could that be understood in an orthodox way? am I missing some context that would make that statement legitimate? Avoid rushing to judgment, but instead exercise circumspection.
Don't be afraid to ask the author what he meant, if you can. This should be done in an honest and forthright way of trying to identify the author's intent. The goal is not to trap the author, but simply to discern what he actually meant by what he said. The goal is not harass or accuse the author, but instead to flesh out the meaning, identify the context, and perhaps define the nuance that the author may have been intending.
With dead or famous authors, this won't always be possible. You may have to investigate for yourself what this person said in the context and on other occasions about the same subject.
When you see a red flag, and you are considering whether this red flag is more than just a red flag, consider the gravity of the fault implied. If the conclusion would be simply that the person is an inexact speaker or has a minor error in doctrine, that's one thing. If the conclusion is that the speaker is a lost person, or a deliberate wolf in sheep's clothing, that's a more serious situation.
The more serious the situation, the more it behooves us to make sure we are correct before leveling a charge. While "innocent until proven guilty" may only be mandatory when you're on a jury, it's a handy reference for us to use in life. Moreover, while for minor things we may simply express a conclusion when we're persuaded it is correct, it would be wise for us to use a higher standard when a more serious charge is being made.
Does charity demand that we always use "beyond a reasonable doubt"? That's not my contention. Rather I'm suggesting that we should use discernment in the use of our tongue. James warns us of the dangers of the uncontrolled use of our tongues. We need to tame that monster, and it's no easy task.
Proverbs 10:19 In the multitude of words there wanteth not sin: but he that refraineth his lips is wise.
Be not rash with thy mouth, and let not thine heart be hasty to utter any thing before God: for God is in heaven, and thou upon earth: therefore let thy words be few. For a dream cometh through the multitude of business; and a fool's voice is known by multitude of words.
When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed. Better is it that thou shouldest not vow, than that thou shouldest vow and not pay.
Suffer not thy mouth to cause thy flesh to sin; neither say thou before the angel, that it was an error: wherefore should God be angry at thy voice, and destroy the work of thine hands? For in the multitude of dreams and many words there are also divers vanities: but fear thou God.