How is Maitre Hauchecorne responsible for his own doom in "The Piece of String"?

Although the old man is entirely innocent of any crime, the local townsfolk still insist that he's guilty, even after it's proved beyond a shadow of a doubt that he couldn't have stolen the pocketbook. This would appear to suggest that Hauchecorne has something of an unsavory reputation in town.
Now of course, it may well be the case that such a reputation is singularly ill-deserved. After all, it's not unusual in small towns for people to be given a bad reputation simply because they don't quite fit in. But in the case of Hauchecorne, one senses that his reputation for deviousness is well-deserved. The way that he conducts himself as he walks down the street, his furtiveness in bending down to pick up the piece of string, and his loud boastfulness at what he thinks is his complete exoneration all convey the impression of a man who simply cannot be trusted—even if, on this occasion, he's completely innocent of any wrongdoing.